国际电工委员会（IEC）规定：凡使用熔断器保护的电动机，应设防止断相的保护装置。
参考答案：对
＿＿＿the people have become the master of their own country＿＿＿science can really serve the people.
A．It is only then； that
B．It was that； when
C．It is only when； that
D．It was when； then
工程施工前，( )需向承包人进行设计交底。
A．委托人B．设计人C．工程师D．发包人
