题目：
When steam is being raised on a boiler, the water level will normally （）.
A.drop as the boiler warms up
B.rise as the boiler warms up
C.remain unchanged until the boiler is hot enough
D.rise and fall with the steam demand
答案：
参考答案：B
When steam is being raised on a boiler, the water level will normally （）.
A.drop as the boiler warms up
B.rise as the boiler warms up
C.remain unchanged until the boiler is hot enough
D.rise and fall with the steam demand
参考答案：B
