冲灰泵投运前不必先开启冲灰泵冷却水门。
参考答案:错
The laser is a very useful means for long-distance communications, the great accuracy in the direction of its beams ______ effective use of small amount of power.
A.makes
B.making
C.made
D.to make
头围是反映孩子大脑发育的重要指标,满1岁时头围约为()
A、45~46
B、47~48
C、32~33
D、40~42