Once an animal expert did some research on antelopes（羚羊）． These antelopes were living on both sides of a river in South America．The expert（1） 　　that the antelopes on the east side multiplied（繁殖）more and ran faster than（2） 　　on the west．

The expert didn't get the reason about differences after thinking hard， as the two groups of antelopes lived in（3） 　　environment and they fed on the same kind of grass．

One year，（4） 　　the help of the Animal Protecting society， he caught ten antelopes on each side and（5） 　　them． A year later， the ten antelopes that were sent to the west side multiplied by fourteen． （6） 　　how about the antelopes sent to the east？ Only three remained!

Where were（7） 　　seven？ They were eaten by wolves．

At last the expert understood why the antelopes on the east were （8） 　　． That was because there were a group of wolves﹣their natural enemy， on the（9） 　　side．

So thanks must go to your opponents（对手）． It is your opponents that are（10） 　　you． It's true!

（1）A． has covered	B． covered	C． has discovered	D．discovered
（2）A． they	B． those	C． them	D．that
（3）A． different	B．same	C． the same	D． difference
（4）A． with	B． without	C． under	D．by
（5）A．changed	B． exchanged	C． challenged	D． fed
（6）A． But	B． Though	C． So	D． Or
（7）A． other	B． the other	C．others	D． the others
（8）A． weak	B．weaker	C． strong	D．stronger
（9）A． south	B． north	C． east	D． west
（10）A． improving	B． hurting	C．comparing	D．disappointing