.有可能成为被控对象的是 (   )

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

B、<span style="font-size:16px;font-family:宋体">流量&nbsp; &nbsp; &nbsp;&nbsp;</span>

C、<span style="font-size:16px;font-family:宋体">加热炉&nbsp; &nbsp; &nbsp;</span>

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