Fill in the blank in the following sentence. _____ is opposite in meaning to the word, 'superior'.

The direct antonym of 'superior' (meaning higher in rank/quality) is 'inferior' (lower in rank/quality). 'Higher' and 'lower' refer to position/height, and 'prior' refers to time/precedence — these are not direct antonyms in the same semantic field. Hence option (3), Inferior, is correct.