You have finished . . . . . . . . last. A. about B. in C. of D. at

The correct answer is: B. in

The word “in” is used to indicate a period of time. In this case, it is used to indicate that the speaker has finished something within a specific time frame.

The other options are incorrect because they do not indicate a period of time.

• The word “about” is used to indicate a rough estimate. In this case, it would not make sense to say that the speaker has finished something “about” last.
• The word “of” is used to indicate possession or a part of something. In this case, it would not make sense to say that the speaker has finished something “of” last.
• The word “at” is used to indicate a specific point in time. In this case, it would not make sense to say that the speaker has finished something “at” last.