将进水阀门开启度减小,使出水温度降低,当低于7℃时,压缩机也应停止运转,这说明()是完好有效的。
A.温度控制器
B.压差控制器
C.水流继电器
D.压力控制器
参考答案:A
已知正方形的面积为25x2+40xy+16y2(x>0,y>0),则表示该正方形的边长的代数式为______.
Missing school to watch the football is quite impossible. Which of the following can replace the underlined part.
A.out of the question
B.out of question
C.without question
D.beyond question