The correct option is A A
The sentence is a general advice and it does not point towards a particular student. Also, the phrase "she or he" confirms that the noun 'student' is non- specific hence we use an indefinite article, 'a' or 'an'. The former article is used for nouns that begin with a consonant, and the latter modifies nouns that begin with a vowel. Since the noun (student) begins with the consonant 's', option A is correct and B is incorrect. The definite article 'the' is used to modify specific and particular nouns. Since the noun 'student' is non-specific, option C is incorrect. 'Some' is a determiner used for countable singular nouns when the noun is particular yet unknown. For example, in "There must be some way of getting out of here" the noun 'way' is unknown, yet there is one specific way referred to here. In the given statement, the noun 'student' is not particular, hence option D is incorrect.