手动隔离开关是一种带熄弧装置的高压电器，能切断负荷电流和短路电流。
参考答案：错
—I wonder how to________to him when I get a present from my foreign friend Jack.
—Of course say "Thank you". [ ]
A. invite
B. answer
C. manage
D. react
浇筑混凝土墙板时，底层应先浇一层厚为()的水泥砂浆或“减半石”混凝土。
A．500mm
B．300mm
C．200mm
D．50～100mm
