坦克履带很宽，这是通过增大_1来_2压强，同时履带上的凸棱是通过增大_3来增大_4

题干

坦克履带很宽，这是通过增大 ____来 ____压强，同时履带上的凸棱是通过增大 ____来增大 ____

上一题下一题 0.0难度选择题更新时间:2014-03-13 04:33:26

受力面积,减小,接触面的粗糙程度,摩擦力

Animals are our good friends. Some are active and others are quiet. But do you know anything about the clever animals in the world? Just have a look!

Animals	Interesting facts
	Kelly is an African elephant. Now she is 19 years old. She lives in the zoo. Kelly has produced more than 100 paintings since last year. She has made over $3,500 for the zoo. Newspaper reporters wrote about Kelly, and then people went to buy her pictures.
	Nana is a clever black and white dog in England. He can do many things just like a human. He can walk on two legs and close the door. Also, he is able to get things for his master, such as newspapers and the TV remote control. What's more, he can sleep and use the quilt very well. No games are difficult for him!
	Koko is a 44—year—old chimpanzee. He has lived with human for tens of years and can “talk” to humans with his hands. He can do simple gestures* and that helps people to understand him.