单选13．热电偶产生的热电势与( )

A、<span style="font-size:16px;font-family:宋体">热电极材料及两端温度有关</span><span style="font-size:16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;"> &nbsp; &nbsp;</span>

B、<span style="font-size:16px;font-family:宋体">偶丝的粗细有关</span>

C、<span style="font-size:16px;font-family:宋体">偶丝的长短有关</span><span style="font-size:16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;</span>

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