Student A: “How long have you been a volunteer for the Red Cross?” Student B: “______________”7/300Mark the letter A, B, C or D on your answer sheet to indicate the sentence that best completes each of the following exchanges. Student A: “How long have you been a volunteer for the Red Cross?” Student B: “______________”When I am 25 years old.By the age of 25.When I was 25 years old.Since I was 25 years old.Giải thíchChọn D