—Why didnt you come to Mike’s birthday party yesterday?---Well I but I forgot it.A. sh

问题补充：

—Why didn you come to Mike’s birthday party yesterday?

---Well, I , but I forgot it.

A. should

B. must

C. should have

D. must have

答案：

A. should

B. must

(答案→)C. should have

D. must have

解析：should have+过去分词可以表示过去应该做而没有做的事情。