A.一級(jí)不宜大于200mm B.二級(jí)不宜大于250mm C.三級(jí)不宜大于280mm D.四級(jí)不宜大于300mm
A.0.22% B.0.42% C.0.62% D.0.82%
A.2 B.3 C.4 D.5