单选题Which of the lists forms of heat transfer, if any, is illustrated by the flow of combustion gases through a boiler?（）ANatural convection onlyBForced convection onlyCBoth natural convection and forced convectionDNone
单选题
Which of the lists forms of heat transfer, if any, is illustrated by the flow of combustion gases through a boiler?（）
A
Natural convection only
B
Forced convection only
C
Both natural convection and forced convection
D
None
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