试指出下列建筑结构哪些是杆件结构()
A、梁
B、挡土墙
C、基础
D、桁架
E、刚架
参考答案:A, D, E
具有固精缩尿,涩肠止泻功效的药物是()
A.金樱子
B.桑螵蛸
C.覆盆子
D.赤石脂
E.乌梅
The teacher urged that all the students ________ their papers carefully.[ ]
A. must check
B. checked
C. check
D. to check