A.1/20 B.1/15 C.1/10 D.1/5
A.水平對(duì)撐或斜撐 B.正交或斜交的平面桿系支撐 C.豎向斜撐 D.環(huán)形桿系或環(huán)形板系支撐
A.2 B.3 C.5 D.6