问题补充：
The professor requested that all the students the reports at once.
A. would hand in
B. hand in
C. handed in
D. handing in
答案：
A. would hand in
(答案→)B. hand in
C. handed in
D. handing in
解析：考查虚拟语气：动词request，require，suggest，advise，command等，后面接宾语从句，从句的谓语用（should）do，句意是：教授要求所有的学生立刻教报告。选B。
