“Isn’t it about time you to do morning exercises？” “Yes it is. Would you like to join us

问题补充：

“Isn’t it about time you to do morning exercises？” “Yes, it is. Would you like to join us？”

A. begin

B. have begun

C. began

D. had begun

答案：

A. begin

B. have begun

(答案→)C. began

D. had begun

解析：考查虚拟语气。It’s time… / It’s high time… / It’s about time… 等后接从句时，从句谓语通常用过去式。选C。