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
独立是高中和大学重要的区别。____ is the major____ between high school and ____.
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