Question 12: Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions: (A) I think you have asked me five (B) or six questions since we (C) have begun (D) this exercise.
Have begun => begin (in the present perfect clause with since in the past tense)
I think you’ve asked me five or six questions since we started this exercise.
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