倒杆翻转法吊装塔类钢结构时，随着塔类钢结构的旋转，起重设备负荷越来越（）。
A、大
B、小
C、一般
D、不变
参考答案：B
—Each year,_ _ fishes are killed by the polluted water and many people are made sick by the polluted air.
—We should do something to stop it! [ ]
A. million of
B. millions of
C. two millions
D. two millions of
测定高速血流需要采用的超声技术是（）
A.A型
B.M型
C.CDFI
D.脉冲多普勒
E.连续多普勒
