问题补充：
Ladies and gentlemen, please fasten your seat belts. The plane .
A. takes off
B. has taken off
C. took off
D. is taking off.
答案：
A. takes off
B. has taken off
C. took off
(答案→)D. is taking off.
解析：考查时态。句意:先生们，女士们，请系好安全带。飞机就要起飞了。Take off是表位置转移的词，经常用现在进行时表将来。所以选D。
