火山爆发、海啸产生时会产生____ 波，倒车雷达利用了____ 波。

语法填空

    July is coming. People all around the world are talking about their ____ (vacation). Parents would like ____ (help) their children relax. ____ (luck), they have two months off. Some people enjoy quiet life, so many of ____ (they) stay at home watching TV, using computers and so on. ____ some spend time differently. My pen pal Tony ____ blonde hair is a boy from the US. He says that ____ (America) like going to the countryside. Just like his big family, they often go to a farm. There, some can feed animals, some can play and ____ (other) can watch ____ nice sky and rivers. They can also taste delicious food. They are quite ____  (interest) in the life there.

风速计是由风叶和改装的电流表构成的．风速越大，风叶转动越快，电流表读数也越大．图中与这一过程的工作原理相同的是（　　）