把方程x²+6x+3=0变形为（x+h）²=k的形式，其中h，k为常数，则k=____ 

如图，直线AB，CD被EF所截，如果∠1与∠2互补，且∠1=120°，那么∠3，∠4的度数各是多少？

根据短文理解，选择正确答案。

Hands play an important part in our daily life. But do you know which of your two hands you use more? Very few people use both hands equally well. Most of us are right-handed. Only about five people out of a hundred are left-handed. New-born babies can take hold of things with either of their hands, but in about two years they usually use their right hands. Scientists don't know why this happens.

Monkeys are our close 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 left-handed ones. Next time you visit a zoo, watch the monkeys carefully, you will see that some of them will use their right hands and others will use their left hands. But most of the people use their right hands better and this makes life difficult for those left-handed people. We live in a right-handed world.