题目

 —Mary knocked into a tree last night while driving, but she is all right. —She is lucky. She _______ herself badly. A. should injure                              B. might injure    C. should have injured                        D. could have injured 答案：D47. Three hundred firemen raced to the hotel after a smoke detector ______ the alarm soon after midnight. A．set offB．set outC．gave awayD．gave off