I ____ my wallet when I was shopping in the store. 

I ____ my wallet when I was shopping in the store. 
A、must have dropped
B、should have dropped
C、could drop
D、ought to have dropped
【正确答案】：A
【题目解析】：本题考查情态动词表推测的用法，Must have done表示对过去情况的肯定推测。题意为我一定是在逛街的时候把钱包丢了，所以应选A.ought to have done/should have done 都表示本应该做却没有做的事