对两端封闭的钢筋混凝土电杆，应先在其（）凿排气孔，然后施焊，焊接结束应及时采取（）措施。
A.一端
B.两端
C.防烫
D.防腐
参考答案：A, D
梯形______一组对边平行．
If we want to cut hair, we should go to . [ ]
A. the kitchen
B. the bathroom
C. the barber shop
D. the doctor's
