离心泵的效率 η 和流量 Q 的关系为    。

A、<em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">Q</span></em><span style="font-size:14px;font-family:宋体">增大，</span><em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">η</span></em><span style="font-size:14px;font-family:宋体">增大</span>

B、<em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">Q</span></em><span style="font-size:14px;font-family:宋体">增大，</span><em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">η</span></em><span style="font-size:14px;font-family:宋体">先增大后减小</span>

C、<em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">Q</span></em><span style="font-size:14px;font-family:宋体">增大，</span><em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">η</span></em><span style="font-size:14px;font-family:宋体">减小</span>

D、<em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">Q</span></em><span style="font-size:14px;font-family:宋体">增大，</span><em><span style="font-size:14px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">η</span></em><span style="font-size:14px;font-family:宋体">先减小后增大</span>