慢性阻塞性肺气肿见（）。
A.胸廓正常
B.桶状胸
C.患侧胸廓膨隆
D.患侧胸廓凹陷
E.心前区局限性隆起
参考答案：B
It has been announced that passengers ____ remain in their seats until the dangerous subjects have been removed.
A．can
B．will
C．may
D．shall
漏电保护器每月至少检查一次，即操作漏电保护器试跳按钮试验一次。
