仅由树木构成的防护林带，风可以从林冠的上方和下方通过，这种林带的结构是______

Because of the poor harvest, wheat prices have ______ in the last six months.

When there are small children around, it is necessary to put bottles of pills out of______.

It is impolite of you to______people when they are in trouble.

设求a，B使f(x)连续．

We regret you that the goods you ordered are out of stock.

For this part, you are supposed to write a letter of refasal in English in 100-120 words based on the following situation. Remember to write it clearly. 你(Li Yuan)的朋友(Jack)邀请你暑期到他家乡——农村去度假。写封信委婉拒绝。信的内容如下： (1)对邀请表示感谢； (2)不能如愿的原因； (3)提出弥补的方式。

我国社会主义发展战略的出发点和归宿是______

简述高斯竞争排除原理及其推论。

CO2在血液中运输的主要形式是______

You cannot ignore the situation forever, one day you will have to______ the consequences of your act.

下列关于心悸的叙述，错误的是______

______ the fact that his initial experiments had failed, Professor White persisted his research.

阅读郭沫若《炉中煤》中的诗句，然后回答下列小题。 啊，我年青的女郎! 我不辜负你的殷勤， 你也不要辜负了我的思量。 我为我心爱的人儿 燃到了这般模样!

(Either) the brother (or) the sister will tell (their) father about (what has happened).

I hear many parents complaining that their teenage children are rebelling. I wish it were so. At your age you ought to be growing away from your parents. You should be learning to stand on your own two feet. But take a good look at the present rebellion. It seems that teenagers are all taking the same way of showing that they disagree with their parents. Instead of striking out boldly on their own, most of them are clutching at (attempting to seize) one another's hands for reassurance. They claim they want to dress as they please. But they all wear the same clothes. They set off in new directions in music. But somehow they all end up crowded round listening to the same record. Their reason for thinking or acting in thus—and—such a way is that the crowd is doing it. They have come out of their cocoons(蚕茧) into a larger cocoon. It has become harder and harder for a teenager to stand up against the popularity wave and to go his or her own way. Industry has firmly carved out a teenage market. These days every teenager can learn from the advertisements what a teenager should have and be. And many of today's parents have come toward high marks for the popularity of their children. All this adds up to a great barrier for the teenager who wants to find his or her own path. But the barrier is worth climbing over. The path is worth following. You may want to listen to classical music instead of going to a party. You may want to collect rocks when everyone else is collecting records. You may have some thoughts that you don't care to share at once with your classmates. Well, go to it. Find yourself. Be yourself. Popularity will come—with the people who respect you for who you are. That's the only kind of popularity that really counts.