Identify the error in the sentence.
Of the three runners, he was the faster.

Correct option is D

Option (d) contains an error.
Detailed explanation of error: When comparing three or more entities, we use the superlative degree, not the comparative. Therefore, the faster should be the fastest. The determiner the correctly precedes a superlative in such of + plural noun constructions. The corrected sentence is: “Of the three runners, he was the fastest.”
Grammatical rule used:
· Comparative (-er / more) is used for two items (A is faster than B).
· Superlative (-est / most + adj) is used for three or more (A is the fastest of all).
· Structure with superlative: of + plural group, use the + superlative.
· Example: Of the four proposals, this is the most feasible.
Information booster / exceptions:
· With exactly two items, use the comparative (the better of the two).
· Some adjectives form irregular degrees (e.g., good → better → best; bad → worse → worst).
· When the adjective is long (three+ syllables), prefer most/least for superlative (the most interesting).