Two categories of grammar words cause the most damage in CDS fill-in-the-blank questions: prepositions and determiners. Not because the rules are complex — but because the traps are extremely precise, and a one-letter difference (like "beside" vs. "besides") changes the entire meaning.
A preposition is a word that shows the relationship between a noun (or pronoun) and the rest of the sentence. That relationship is usually about position, direction, time, or manner — but in English, it is also heavily governed by fixed collocations that have no logical explanation. You say "on the Internet" not "in the Internet", and you "enter into an agreement" not "enter in an agreement". No rule produces these — only pattern recognition does.
A determiner is a word that comes before a noun to specify it: which one, how many, whose. Articles (a, an, the) are determiners. So are quantifiers like "some", "any", "few", "little", "each", "either", "both", and "all". The errors CDS tests are almost always about choosing the right quantifier based on two factors: (1) whether the noun is countable or uncountable, and (2) whether the sentence is affirmative, negative, or interrogative.
Think of determiners as a filter dial with two axes. On one axis: count-ability. On the other: tone (positive/negative/neutral). The wrong determiner means you have the dial set incorrectly — the sentence sounds wrong to any native speaker even if the meaning seems close.
Here's a useful analogy. Prepositions are like the connectors in a circuit — they must be the right type for the specific device (verb or noun) they connect to. You can't use a USB-A connector where a USB-C is needed, even if both are "connectors". Similarly, you can't use "beside" where "besides" is needed, even if both look almost identical.
Most CDS candidates lose marks here not because they don't know the words, but because they haven't catalogued the specific fixed expressions and quantifier-noun agreements that the exam tests repeatedly.
The honest truth about English prepositions is that many of them cannot be derived from rules — they are fixed pairings. For CDS, the most tested category is verb/noun + preposition collocations.
High-frequency fixed phrases for CDS:
| Expression | Correct Preposition | Wrong Options Often Given | |---|---|---| | on the Internet | on | in, at, with | | enter into an agreement | into | in, at, unto | | arrive at (a place) | at | in, on | | arrive in (a city/country) | in | at, on | | responsible for | for | of, to | | interested in | in | for, at | | depend on | on | in, upon (both acceptable) | | beside (next to) | — | besides (= in addition to) | | besides (in addition to) | — | beside (= next to) |
The "beside" vs. "besides" distinction is a classic CDS trap. "Beside" is purely spatial — "stand beside me" means "stand next to me." "Besides" means "in addition to" or "apart from" — "what else do you play besides hockey?" If you substitute "beside" in that sentence, it implies hockey is a physical location, which is absurd.
Prepositions of Time — the in/on/at system:
Prepositions of Place — in/on/at:
Every quantifier decision in CDS comes down to this chart:
| | Countable (Plural) | Uncountable | |---|---|---| | Positive | many, a few, several, both, few* | much, a little, little* | | Negative/Question | any, no | any, no | | Distributive (each/every) | each, every, either, neither | — | | Universal | all | all |
*"Few" (without "a") has a negative sense: "few people came" = hardly any. "A few" is positive: "a few people came" = some did. *"Little" (without "a") has a negative sense: "little time remains" = barely any. "A little" is positive.
The "any" rule — three distinct uses:
Each vs. Every vs. All:
Either vs. Both vs. Neither:
These three only work with a group of exactly two:
When the noun is singular and you're talking about two things, "either" is correct — not "both" (which requires plural "sides") and not "all" (which is for three or more).
The Internet is conceptualised in English as a surface or a network you travel across, not a container you go inside. Apply this mental image: you go "on" a bus, "on" a plane, "on" a road — all surfaces or networks. You go "in" a car, "in" a room — enclosed spaces. The Internet is open and network-like, so it's always "on the Internet." This immediately eliminates "in" and "at" as options. Standard method: read all four options, second-guess yourself (30s). With this rule: eliminate "in", "at", "with" in 3 seconds, pick "on."
Whenever you see "little" or "few" without the article "a", treat the sentence as carrying hidden bad news. "She has little time" = she barely has any — that's bad. If the context is busy/stressed/lacking, you want "little" (uncountable) or "few" (countable) without "a". If the context is hopeful or sufficient ("she managed to find some time"), you want "a little" or "a few." In the Dr. Kumar question: she is "very busy" — the context is negative/stressed, so "little" (not "a little") is correct. This eliminates two options in one read. Step count: 4 steps with normal analysis → 2 steps with the negativity signal.
Before picking between "either", "both", "neither", and "all", count the things being referenced. A street has two sides — so "all" is immediately wrong (requires 3+). Now check the sentence tone: if affirmative and "one of the two", use "either." If "both together", use "both" but check the noun is plural. "You can park on either side" — singular "side", open choice between two → "either". "Both" would require "both sides." This saves roughly 20 seconds of hesitation: the moment you count exactly two, "all" and "some" are gone.
Think of the "s" in "besides" as standing for "something extra" — it means "in addition to." No extra "s", no extra meaning: "beside" is purely spatial (next to). When the sentence asks about an additional thing or another option ("what other sport... besides hockey"), the "s" must be there. When describing physical proximity ("sit beside me"), no "s." Test: replace the word with "in addition to." If it fits, use "besides." If it doesn't, use "beside." This reduces a confusing look-alike pair to a single substitution test — roughly 15 seconds faster than re-reading context four times.
Fixed collocation: you always "enter into" an agreement, a contract, a negotiation, a relationship. The "into" signals movement from outside to inside a formal arrangement. "Enter in" and "enter at" do not exist as standard collocations. "Unto" is archaic and appears only in religious or legal texts from earlier centuries. The moment you see "entered _____ an agreement," write "into" without looking at the other options. Store it as a single unit: enter-into-agreement. This is a 3-second pick versus 25 seconds of option-by-option analysis.
When you hit a preposition or determiner blank in CDS, run this decision tree in under 20 seconds:
Step 1 — Identify the category. Is the blank asking for a preposition (showing relationship between noun/verb and rest of sentence) or a determiner (coming before a noun to quantify or specify it)?
Step 2 — For prepositions: Is there a verb or noun in the sentence that has a fixed collocation? (enter into, interested in, on the Internet, besides/beside). If yes, apply the fixed phrase immediately. If no fixed phrase, apply the in/on/at spatial or time rules.
Step 3 — For determiners: First, is the noun countable or uncountable? Eliminate options that violate this (few/many = countable; little/much = uncountable). Second, is the sentence positive, negative, or interrogative? "Any" in negative/question vs. "any" as universal in affirmative with singular noun — check the noun number. Third, how many items are in the reference group? Two = either/both/neither. Three or more = all/some.
Step 4 — Eliminate by grammar first, meaning second. Grammar rules (noun count-ability, singular/plural agreement) cut options faster than meaning analysis.
Why this question: Tests the most common fixed prepositional collocation in CDS — medium + preposition, specifically digital media.
Solving path: The Internet is a network/surface, not a container. Apply the surface rule: "on." Eliminate "in" (enclosed space), "at" (specific point), "with" (association). Answer: on. Time: 5 seconds.
Why this question: Tests the negative-sentence use of "any" with a countable noun, and the trap of choosing "much" or "many" with "more."
Solving path: Sentence is negative ("don't want"). In negative sentences, use "any" for both countable and uncountable. "Much more" and "many more" are not idiomatic here with this structure. "One more" changes meaning entirely. Answer: any. Time: 8 seconds.
Why this question: Tests the beside/besides confusion — a classic one-letter trap that CDS has returned to multiple times.
Solving path: Substitute "in addition to hockey" — it fits. So "besides" (with s) is correct. "Beside" = next to (spatial). "Instead" requires "instead of." "Expect" is a verb, not a preposition. Answer: besides. Time: 6 seconds.
Why this question: Tests "each" vs. "all/some/any" in a context emphasising individual repeated instances.
Solving path: "Two or three times" establishes multiple instances. The sentence emphasises that on every single individual occasion, no one responded. "Each time" = individually, one by one. "All time" is ungrammatical. "Some time" contradicts "no one responded" in the context. "Any time" doesn't fit the "every instance" meaning here. Answer: each. Time: 10 seconds.
Why this question: Tests either/both/all with exactly two items and a singular noun — three traps in one question.
Solving path: A street has two sides — eliminate "all" (3+). "No" changes meaning to prohibition. "Both" requires plural "sides." "Either" works with singular "side" and means "one of the two, your choice." Answer: either. Time: 8 seconds.
Why this question: Tests the little/a little distinction with an uncountable noun in a negative context.
Solving path: "Time" is uncountable — eliminate "few" and "a few." Context is negative (very busy). "Little" = hardly any (negative). "A little" = some (positive). Busy doctor has barely any time → "little." Answer: little. Time: 8 seconds.
Why this question: Tests the affirmative + singular countable noun use of "any" meaning "every one without exception."
Solving path: The noun is singular "student." "All", "Some", "Few" all require plural "students" — eliminate all three on grammar grounds alone. "Any" with singular countable noun in affirmative = "every one, it doesn't matter which." Answer: Any. Time: 6 seconds — grammar elimination alone solves it.
Why this question: Tests a high-frequency fixed collocation — enter into an agreement.
Solving path: Fixed collocation: "enter into an agreement." "Unto" is archaic. "Enter at" and "enter in" are not standard. Store the unit: enter-into-agreement. Answer: into. Time: 4 seconds.
Confusing "beside" with "besides." These are two different words with different grammatical functions. "Beside" is always spatial. "Besides" means "in addition to" or "apart from." Writing "beside hockey" in a question about additional sports is a meaning error, not just a spelling slip.
Using "few/many" with uncountable nouns. "Time", "information", "advice", "water", "patience" — these are uncountable. You cannot have "few time" or "many information." The correct pair is "little/much." This error appears in roughly one question per CDS paper in some form.
Using "both" with a singular noun. "Both side" is ungrammatical — "both" always demands a plural noun. When the noun is singular and you're choosing between two options, "either" is the correct determiner.
Missing the affirmative "any" with singular countable nouns. Most candidates know "any" in negative sentences. The CDS-specific trap is "any student could tell you" — affirmative, singular, meaning universal. Candidates incorrectly choose "every" or "all" here without checking noun number.
Treating "each" and "every" as interchangeable. They are close but not identical. "Each" separates individuals and is often used for smaller, more specific groups with emphasis on separate occasions or items. When the sentence counts individual instances (each time I called), "each" is mandatory, not "every."
Using "unto" or "in" with "enter." "Unto" belongs to archaic English. "Enter in an agreement" is non-standard. The fixed collocation is "enter into" — no variation is acceptable in standard modern English, which is what CDS tests.