A.1/2B.1/3C.1/4D.1/5
A.不應(yīng)低于C15或M15 B.不應(yīng)高于C15或M15 C.不應(yīng)低于C25或M15 D.不低高于C20或M15
A.15MPa B.10MPa C.7MPa D.5MPa