The correct answer is A. has finished.

1. Has finished: This option is correct because it uses the present perfect tense, which is appropriate for indicating that the action of finishing the speech has been completed by the subject (in this case, "your friend and mentor"). The subject here is singular (one person), so the singular form "has" is used.

2. Was finished: This option is incorrect because it is a passive voice construction. The sentence needs to be in the active voice where "has finished" is the correct form.

3. Have finished: This option is incorrect because "have" is used with plural subjects or with "I" and "you" in the present perfect tense. Here, "your friend and mentor" is singular, so "has" should be used instead.

4. Are about to finish: This option is incorrect because it indicates an action that is expected to happen soon, but the sentence is referring to an action that has already been completed.

Summary:

- A. has finished is the correct choice because it properly uses the present perfect tense to describe an action completed by the subject.