The correct option is 'a'. Although the word 'university' begins with the vowel letter 'u', it is pronounced with a consonant sound 'yu' (like the sound in 'yellow' or 'you'). We use the article 'a' before words starting with a consonant sound. 'An' is incorrect because it is only used before vowel sounds. 'The' is incorrect because we are speaking of a student in a general sense, not referring to a specific, unique student.