短文改错 (共10小题；每小题1分，满分10分)

Last weekend I went to the Summer Palace as usually. At about noon, I was enjoying my reading near a lake while suddenly I hear someone crying for help. I went up to see what was happening. I was shocking to find a little child struggling in the water in the distance while many peoples were standing by without doing anything. Without any hesitation, I had pushed through the crowd as I took off my coat, but jumped into the water quickly. I managed to reach him and carried him back to safety. To his great relief, the kid was saved. I was proud what I had done. I wish everyone could give the hand when someone else is in need.

用压缩空气作能源的仪表称为（）仪表。

A.气动

B.电动

C.自动