为了适应环境的变化而增加或修改系统部分功能的维护工作属于（）
A. 完善性维护
B. 适应性维护
C. 更正性维护
D. 预防性维护
查看答案
How to reply when the passengers press the call button?
A. What can I do for you?
B. Here you are.
C. Nice to meet you.
D. Welcome aboard.
（中译英）我们提供多种类型的音乐。We provide several kinds of music.
A. 对
B. 错
UM refers to ( ).
A. unavailable minor
B. unaccompanied man
C. unaccompanied minor
D. unavailable man
What would be provided for unaccompanied child on the plane?
A. child packs
B. child meal
C. milk powder
D. pacifier
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