施工升降机封闭式吊笼顶部应有紧急出口应装有向()开启的活板门,并设有电气安全开关,当门打开时,吊笼不能启动。
A.内
B.外
C.均可
D.随意
参考答案:B
It's not so _____ as yesterday, so there are _____ people sitting in the square. [ ]
A. cold; fewer
B. warm; more
C. cold; more
D. warmer; fewer
丈量两点间的距离必须在两点间的直线上进行。( )