消防员呼救器分为普通型消防员呼救器和无线通信消防员呼救器两种。
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新焊装下拉杆头的搭接量不得小于()。
A. 50mm
B. 65mm
C. 80mm
D. 85mm
同型号不同测量范围的差压变送器是由于测量膜片的()不同决定的。
按水文循环的规模和过程不同,水文循环可分为()循环和()循环。
All items such as steam pipes, exhaust pipes and fittings which, because of their location and operating temperature, present a hazard should be adequately lagged.That means the items should()
A. not be put into operation too early
B. be pay adequate attention to
C. be used only when necessary
D. be coated with certain material