Some of my friends ______________ volunteer work for many years, but I only ______________ last summer.
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Some of my friends ______________ volunteer work for many years, but I only ______________ last summer.
A. are doing/ have started
B. have done/ started
C. have done/ have started
D. did/ started