Some of my friends ______________ volunteer work for many years, but I only ______________ last summer.Đoạn văn6/45Mark 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. are doing/ have startedhave done/ startedhave done/ have starteddid/ startedGiải thíchChọn B