阅读短文,用方框内所给单词的适当形式填空,使短文意思通顺,完整.请将答案写在短文后相应题号的横线上.注意：1.每个单词只能用一次；2.每空限填一词,有些词需要做相应的变化；3.其中有两个多余选项。

succeed，they，work，careful，make，so，happy，close，one，few，either，but

Do you use your right hands more or left hands more? Very___71___of us use both of our hands well. Most people use right hands. Only about five people of a hundred use left hands. New-born babies can take things with__72___of their hands,___73___in about two years, they like to use___74___right hands. Scientists don’t know why this happens. They’ve studied it. They think our animal ancestors used their right hands, this may not be true. Monkeys are our__75___relatives in the animal world.     
Scientists have found that monkeys like to use one of their hands more than the other----but it can be either hand. There are as many right-handed monkeys as the left -handed___76___. Next time you visit the zoo and do watch the monkeys__77__. You’ll see that some of them will use their right hands and others will use their left hands. But men use their right hands better and this ___78___life difficult for the left-handed ones. We live in a right-handed world. Some scientists have found out that more of __79__people are left-handed, but they don’t know why. But they are _80_hard to discover the secret.
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