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 corrosion