Select the most appropriate option to fill in the blank.
The students were keen _________ participating.
Show answer & explanation
Correct answer: A
Explanation
Adjective-Preposition Collocation: In English, the adjective "keen" is typically followed by the preposition "on" when it is followed by a gerund (a verb ending in -ing) to express interest or enthusiasm.
Sentence Structure: In the sentence "The students were keen on participating," the word "participating" is a gerund.
Common Usage: While "keen to participate" (using an infinitive) is also correct, when choosing between prepositions to precede an "-ing" form, "on" is the standard idiomatic choice.