简述热探测器的工作原理。
参考答案：
当探测器安装位置周围温度升高超过88℃，则温度传器中的双金属片动作使接触器闭合，电流通过，发出报井信号。
霉菌形成的菌落常呈绒毛状、絮状或蜘蛛网状，与培养基结合紧密。[ ]
After the war, a new school building was put up ___________there had once been a theatre.
A．that
B．where
C．which
D．when
