Next weekend, I . . . . . . . . my proficiency exam, so I . . . . . . . . more or less 300 questions so far.

The correct answer is: E. will have/have finished

The sentence is about a future event (taking the proficiency exam next weekend) and a past event (having finished more or less 300 questions so far). The correct verb tense to use for a future event is the future perfect tense, which is formed with the auxiliary verb “will have” and the past participle of the main verb. The correct verb tense to use for a past event is the simple past tense, which is formed with the past tense form of the main verb.

Here is a breakdown of each option:

• A. am going to have/finished is incorrect because the future perfect tense should be used to talk about a future event.
• B. am having/will have finished is incorrect because the simple present tense should be used to talk about a current event.
• C. am to have/finish is incorrect because the infinitive should be used to talk about a future event.
• D. am having/will finish is incorrect because the simple present tense should be used to talk about a current event.
• E. will have/have finished is correct because the future perfect tense should be used to talk about a future event and the simple past tense should be used to talk about a past event.

I hope this explanation is helpful!