单选题When steam is being raised on a boiler, the water level will normally （）.Adrop as the boiler warms upBrise as the boiler warms upCremain unchanged until the boiler is hot enoughDrise and fall with the steam demand
单选题
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
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