A.1.5 B.2.0m C.2.5m D.3.0m
A.75% B.80% C.85% D.90%
A.預(yù)應(yīng)力混凝土管 B.預(yù)應(yīng)力鋼筒混凝土管 C.自應(yīng)力混凝土管