---Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben?

　 --- No, we ______ it. But we had a lot of traffic on our way.

　 A. could have attended　　 　　　　　　　　 B. must have attended

　 C. could attend　　　　　 　　　　　　　 D. shouldn't have attended

 ---Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben?

   --- No, we ______ it. But we had a lot of traffic on our way.

   A. could have attended                                    B. must have attended 

   C. could attend                                          D. shouldn't have attended

—Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben?

   — No, we ______ it. But we had a lot of traffic on our way.

   A. could have attended                                    B. must have attended 

   C. could attend                                          D. shouldn't have attended

---Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben?

   --- No, we ______ it. But we had a lot of traffic on our way.

   A. could have attended                                              B. must have attended 

   C. could attend                                                    D. shouldn't have attended

 ---Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben?

   --- No, we ______ it. But we had a lot of traffic on our way.

   A. could have attended                       B. must have attended 

   C. could attend                              D. shouldn't have attended