單項(xiàng)選擇題
A.1/200-1/300 B.1/500-1/600 C.1/1000-3/1000 D.1/2000-1/4000
A.次梁 B.主梁 C.上梁 D.下梁
A.大于 B.小于 C.等于 D.不大于