高空作业的安全措施中,首先需要（）
A. 安全网
B 安全带
C. 合格的工作台
Paragraphs 2 and 3 explain ________.
A. those good things are not without side effects
B. why clever advertising is so powerful
C. why in modern times self-medication is still practised
D. why people develop faulty ways of life
DCS操作画面中,M对N表示自动,对UTO表示手动（）
One reason why colleges increase tuition and fees is that the state support is shrinking.（）
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