Fill in the blanks (X, Y) in the following sentences with the appropriate word/phrase given in the brackets: I. I spent X (less/the least) money on clothes in the whole family. II. The people who work the hardest make Y (a few/the fewest) mistakes.

Both sentences involve comparisons among a group (the whole family in I, and a group of workers in II), requiring superlative forms. In sentence I, 'the least' is the superlative of 'little' (used with uncountable nouns like 'money') and indicates the smallest amount among the whole family. In sentence II, 'the fewest' is the superlative of 'few' (used with countable nouns like 'mistakes') and indicates the smallest number of mistakes. Therefore, the correct combination is I—the least, II—the fewest.