Explanation:
The sentence is a reported question, and in reported speech, when the reporting verb is in the past tense (as "asked" is in this case), we typically change the tense of the verb in the direct question to the past perfect tense.

Had is the past perfect form and is used here because the teacher is asking about an action that might have happened before the time of speaking (i.e., whether she had already seen her boyfriend).

Why the other options are incorrect:

A. has – "Has" is the present tense form, which does not fit because the reporting verb "asked" is in the past tense, so the verb should be in past perfect.

B. have – "Have" is incorrect because it does not agree with the subject "she." "She" requires the singular form "had."

C. was – "Was" is the past simple tense, which wouldn't work in this context because the reported speech is talking about something that happened before the question was asked.

E. will have – "Will have" is the future perfect tense, which is inappropriate here because the question is about something in the past.