Options A and B: 'Has' as an auxiliary verb is paired with the main verb in order to determine the tense of the sentence.
'Has' is used when the subject is in the third person singular narrative. In contrast, 'have' is used for the third person plural narrative (it's also used for the first and second narratives, both in the singular and plural form).
The subject in the given sentence "each of the students" is singular as 'each' lays emphasis on each student. Hence option A is correct and B is incorrect.
Option C: 'Will' is used in the future tense. It is followed by the auxiliary 'be' and not 'been', as given in this sentence. Hence C is incorrect.
Option D: 'Are' is a form of 'to be'. 'Be' has many forms: is, are, was, been, etc.
Since the verb form of be, been, has already been used, 'are' is not required. Hence D is incorrect.