A vessel is constructed with a steel hull and an aluminum superstructure. Which statement is TRUE?（）
A. The aluminum will provide greater resistance to the spread of fire by conduction
B. The aluminum structure is usually attached to a steel coaming by a method that insulates the two metals
C. If the superstructure is stressed，an aluminum structure requires additional expansion joints to prevent fracture
D. The steel at the area of the aluminum-to-steel connection must be closely checked for galvanic corrosio
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