The correct answer is a.
The word “a” is used before singular nouns that are not specific. In this case, the speaker is not referring to a particular university student, but rather any university student in general.
The word “an” is used before singular nouns that begin with a vowel sound. In this case, the word “university” begins with a consonant sound, so “an” would not be the correct answer.
The word “the” is used before singular nouns that are specific. In this case, the speaker is not referring to a particular university student, so “the” would not be the correct answer.
The word “any” is used before singular nouns that are indefinite. In this case, the speaker is referring to any university student in general, so “any” would not be the correct answer.