问题补充:
While watching TV, .
A. the doorbell rang
B. the doorbell rings
C. we heard the doorbell ring
D. we heard the doorbell rings
答案:
A. the doorbell rang
B. the doorbell rings
(答案→)C. we heard the doorbell ring
D. we heard the doorbell rings
解析:可联系答.案.网客服索取。