下列电器设备在工作过程中，把电能转化为机械能的是（　　）

如图，从气球A上测得正前方的河流的两岸B，C的俯角分别为75°，30°，此时气球的高是60m，则河流的宽度BC等于（　　）

完形填空。

    A boy and a girl catch a bird and 1 it in a birdcage (鸟笼）. They like it 2 and 3 it every day. A cat sees the bird and wants 4 her supper. 5 the bird is in the cage. She can't catch it. So she is very 6.

    One day, she opens the door of the cage 7 wants to catch it. But the bird flies away. The cat 8, and she has 9. The two children 10 and　see the bird isn't in. They are very angry and put the cat into the cage.

史学界有人评价康有为的《新学伪经考》，是“跪着向封建制度造反”，主要是因为康有为借助该书（    ）