apply for
A. 申请
B. 运用
C. 为…道歉
D. 申请信
It is a little difficult for me to____the problem.
A. answer
B. answering
C. answered
D. answers
Qian Xuesen devoted all his life to______scientific research.
A. do
B. doing
C. did
D. does
He told his students to be careful next time. 其中to be careful做什么成分?
A. 宾语
B. 宾语补足语
C. 间接宾语
D. 直接宾语