When you find the engine is hotter than normal, you should ______.

A．drive to a service station to get a cool engine

B．turn off your heater so as to cool down the engine

C．switch on the heater as soon as possible

D．try to make the engine boil over ______.

可以用E-R图描述的是（）。

A.逻辑模型

B.概念模型

C.物理模型

D.数据模型