七、短文填词。根据短文大意，填入恰当的单词。（20分，每空2分）

Many useful machines were __77__ by inventors. These machines have __78__

the world a lot. There are many great inventors in the world, and Watt was one of them.

Watt was English. When he was a child, he liked to ask questions and he was always __79__hard. One day, he was sitting in the kitchen with his grandmother, he __80__ a kettle(水壶) on the stove(火炉). Soon steam(蒸汽) began to come __81__ the kettle and the lid(盖子) was shaking. Watt asked what was in the kettle. His grandmother said, “Water, my child.”“But I know there’s __82_ in it. It pushes the lid up.” said Watt. His grandmother told him that it was only steam. He asked his grandmother,“__83__ does the steam come up under the lid?”His grandmother said that it came from hot water. Watt said to __84__ ,“The steam will be much strong. It can push things. The steam will be much __85__ if there’s more water.”Later, Watt tried hard and made steam __86__ for people. He invented the first engine.

77、      78、         79、      80、     81、       

82、      83、         84、      85、     86、      

电气伺服进给系统驱动部件是指（）等。

A.步进电动机

B.直流伺服电动机

C.交流伺服电动机

D.液压型电机

E.直线伺服电动机