单选4．Cu50的输出信号为(   )

A、<p style="line-height: 150%;"><span style="font-family: 宋体;">电压</span><span style="font-family: &#39;Times New Roman&#39;, serif;">&nbsp; &nbsp; &nbsp;</span>

B、<span style="font-size:16px;font-family:宋体">电流</span><span style="font-size:16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp; &nbsp;</span>

C、<span style="font-size:16px;font-family:宋体">电阻值</span><span style="font-size:16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp;&nbsp;</span>

D、<span style="font-size:16px;font-family:宋体">温度</span>