The mother along with her children in the supermarket when the explosion happened.
A. was shopping
B. were shopping
C. have been shopping
D. had shopped
网友回答
A. was shopping
B. were shopping
C. have been shopping
D. had shopped
解析：考查主谓一致和固定句型。固定句型be doing sth when…正在做某事在这时发生了意料之外的事情；故使用进行时，另外本题的主语是The mother along with her children，谓语动词应该与the mother保持一致，使用单数形式。故A正确。