问题补充:
The plane of the Polish president was about to land it snagged(挂) treetops and crashed, the president and 96 others on board.
A. while, killed
B. when, killing
C. and, and killed
D. when, to kill
答案:
A. while, killed
(答案→)B. when, killing
C. and, and killed
D. when, to kill
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