问题
选择题
With a lot of tough problems _____, the pilot was still calm, cool and collective under pressure. [ ]
A. solve
B. solved
C. solving
D. to solve
答案
答案：D
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With a lot of tough problems _____, the pilot was still calm, cool and collective under pressure. [ ]
A. solve
B. solved
C. solving
D. to solve
答案：D