单项选择题
Undercoats are used （）the primer before the topcoat.
A.in B.over C.to D.with
单项选择题 Primer coats are applied to a bare metal surface to （）protection against rust.
单项选择题 Primer coats are applied to a bare metal surface to give protection against （）.
单项选择题 （）is used in bilges and peak tanks.
