“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
网友回答
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。