A.1/200 B.1/400 C.1/1000 D.1/500
A.1m B.1.2m C.1.5m D.2m
A.應(yīng)先安裝縱向水平桿,后安裝橫向水平桿 B.應(yīng)先安裝橫向水平桿,后安裝縱向水平桿 C.隨意無順序 D.A和B