问题
选择题
________it have been the failure to pick up directi
ons from the ground control that caused the air crash?[ ]
A. Must
B. Could
C. Would
D. Should
答案
答案：B
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________it have been the failure to pick up directions from the ground control that caused the air crash?[ ]
A. Must
B. Could
C. Would
D. Should
答案：B