升压时，沸腾式省煤器应打开再循环门，非沸腾式省煤器可以开启旁通烟道。
参考答案：对
Over the years the European Union has made great efforts to _______ the safety of food and protect the health of its people.
A．discover
B．ensure
C．revise
D．react
润滑油的注入量一一般控制在轴承箱液面计的（）。
A．红线顶部
B．红线下
C．两红线之间
D．任意位置，看见即可
