A. they have been exposed B. if they have been exposed C. having been exposed D. to exposeĐoạn văn16/83Mark the letter A, B, C, or D on your answer sheet to indicate the correct option that best fits each of the numbered blanks from 13 to 18. they have been exposed if they have been exposedhaving been exposed to exposeGiải thíchChọn đáp án B