Height is just one of the thousands of features your genes (基因) decide. In fact, because you have two parents, your genes provide you a height that usually lands somewhere between the height of each parent. If both your parents are tall, then maybe you will be tall, too, but if you have questions about how tall you're going to be, ask your doctor if he or she can help you find it.

    But genes don't decide everything. For example, eating an unhealthy diet can keep you from growing to your full potential (潜力). Getting enough sleep and enough exercise will help you grow to the right height.

    No doubt (怀疑) you're wondering how fast you should grow .It depends. There's no perfect or right answer. Kids grow about 2 inches (5 centimeters) a year between age 3 and the time when they start puberty (when your body starts changing and becoming more grown up). Your doctor will know how your growth has been going over the years. 2 centimeters here and 2 inches there are not nearly as important as the height you're at now, how you've been growing up to this point, and what other changes your body may be going through.

    Don't be scared if you seem to have grown a lot in a very short time. Everyone has a growth spurt (高峰) during puberty. The age for starting puberty is about 10 for girls and about II for boys. But it can be earlier or later-between 7 and 13 for girls and 9 and 15 for boys.

    You'll usually begin to notice that you're growing faster about a year or so after your body starts to show the first changes of puberty.

Companies these days spend thousands of dollars on their computer security. They buy the best firewalls and computer programs. However, Kevin Mitnick thinks the biggest danger these days is not a weakness in technology.

In the 1990s, Kevin Mitnick was an infamous hacker (黑客). He hacked into government and corporate computer systems. After being punished and sent into prison, Mitnick decided to use his skills in a different way. He started his own computer security firm. He now advises people on how to keep their computers safe.

According to Mitnick, the biggest danger to security is people. However, by this he doesn't mean hackers. In fact, he means the people using the programs. "If an attacker can get one trusting person to give his or her information, the attacker gets in. All that money spent is basically wasted." A hacker can get around everything with just one person within the company.

Unfortunately, people are still too trusting. In a recent test of the US tax office (the IRS), security experts called 100 managers. They posed as IRS computer technicians. The experts were able to fool 35 of the managers. They gave both their passwords and IDs. In the hands of real hackers, this would have been a disaster!

Scientists have always wanted to know more about the universe and they are working hard.

 {#blank#}1{#/blank#}(year) ago they knew many things about the moon.  {#blank#}2{#/blank#}they knew how big it is and how far it is from the earth, they wanted to know more about it. They thought sending people to the moon was the best way.

The moon is about 384,000 kilometres away  {#blank#}3{#/blank#}the earth. A plane cannot fly to the moon  {#blank#}4{#/blank#}the air is too thin at high altitude(海拔) to support the plane.

Then the scientists tried  {#blank#}5{#/blank#}(they)best to invent something that can fly even when there is no air. That is a rocket(火箭).

How does a rocket fly? There is gas(气体)in the rocket. When  {#blank#}6{#/blank#}gas is made very hot inside the rocket, it will rush out of the end of the rocket, so it can make the rocket fly up  {#blank#}7{#/blank#}(quick) into the sky.

Rockets can fly into space, Rockets with people in them  {#blank#}8{#/blank#}(be) to the moon already. Several rockets without people in them have flown to another planet much  {#blank#}9{#/blank#}(far) than to the moon. One day rockets may be able  {#blank#}10{#/blank#}(go) to any place in space. Let's hope for the coming of that day.

Before "summer homework deferral period" came out，I used to

……

Every town in America has a post office. Some are very t{#blank#}1{#/blank#} at the corner (角落) of a shop. You may be u{#blank#}2{#/blank#} of them. Others are large buildings. In the post office, stamps are sold at any window. The post offices sell stamps at different p{#blank#}3{#/blank#}, from one cent to some dollars. In a{#blank#}4{#/blank#}, you can also buy postcard in the post office. It is more e{#blank#}5{#/blank#} to send a letter than a postcard. It always cost you twice more of the price.