4."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
正确答案是C
4."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
正确答案是C