Height is just one of the 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 most probably 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 them out.

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

    It's natural that you're wondering how fast you should grow. There's no perfect or right answer. Generally speaking, kids grow about 6 cm a year between age 3 and the time when they start puberty.

    Your doctor will know how your growth has been going over the years. 2 cm here and 3 cm there make a little difference to the height you're at now. How have you been growing up to this height? What other changes may your body be going through?

    Don't be amazed 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 11 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 after your body starts to show the first changes of puberty.

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    There are over 37 000 known kinds of spiders（蜘蛛）in different shapes and sizes in the world. The largest spiders live in the rain forests of South America and are known as the "bird-eating" spiders. These spiders can grow up to 28cm long and they eat small birds. The smallest spiders are from Western Samoa. These tiny spiders are less than 0.5mm long. They live in the plants that grow on mountain rocks.

    Some people like to keep spiders as pets but most people don't like touching them. A great number of people are afraid of them mainly because of their poison—something will make them hurt or even die. But in fact, only thirty kinds of spiders are very dangerous to humans. Spiders provide benefits for humans by catching and eating insects such as flies and mosquitoes (蚊子).

    Spiders are different from other animals because they make webs to catch the small insects for food. The special silk of a spider's web is light and strong—five times(倍)stronger than steel. Some people have tried to raise spiders in order to collect their silk but no one was successful in doing it. One reason is that it takes 670 000 spiders to produce half a kilo of silk and all of these spiders need living insects for their food. Besides, spiders are usually solitary (独自的) animals and they need keeping alone.

    All in all people are amazed to learn that there are so many secrets in spiders!

Summer is almost here. It's a great time to go out and play. But take care. The weather gets hot, too much sun is unhealthy. How can you stay healthy this summer?Follow these tips.

Drink water.Hot weather makes you sweat(出汗). Your body needs more water to keep you cool and stay healthy. Drink lots of it, even when you are not thirsty.

Pick the right clothes. Make sure they are white color or light color and a little big.

Wear sunscreen. The sun's rays are stronger than you think.Sunscreen can stop some of those rays. Look for SPF30 or higher.

Listen to lifeguards. Lifeguards work at beaches and pools.They help us stay safe in the water.

Tourism has become a huge industry. Tourists make millions of foreign trips a year, twice as m {#blank#}1{#/blank#}as 20 years ago. It's now the largest employer on Earth. Clearly, it can do great good, but it can also do great damage.

It's true that tourism has brought benefits to many areas of the world that were very poor. However, mass tourism also has some bad e {#blank#}2{#/blank#}. Local culture and customs change as more tourists arrive. Too much tourism damages the environment. And more and more tourists are behaving badly.

Complaints from local people are growing. In cities such as Barcelona or Venice residents say that too many tourists arrive on cruise ships(游轮). As a result, town centres are overcrowded. They tell stories about n {#blank#}3{#/blank#} parties that keep people awake all night. In famous beauty spots, where tourist money was welcomed, people are now worried about the damage tourists do to the environment.

Of course, many tourists enjoy the benefits of tourism in a responsible way. They choose holidays that support the local economy and they respect the local culture and the environment. Environmentally friendly tourism, or eco-tourism, is becoming more p {#blank#}4{#/blank#}.

Responsible tourist behaviour is necessary, but it isn't enough to solve the problem. Many people now believe that governments should control how many visitors enter their country. They believe they should limit the n {#blank#}5{#/blank#}of cruise ships that use their ports and should not allow too many hotel developments.

U {#blank#}6{#/blank#}, governments are in a difficult situation. Tourism brings in a lot of money and this helps them i {#blank#}7{#/blank#} life for the local people. However, some governments are beginning to understand that too much tourism can be bad for the local population and the environment. They've taken some measures to promote environmentally friendly tourism. There may still be hope.

 The Chinese abacus is known as the suanpan. It is {#blank#}1{#/blank#} important part of traditional Chinese culture and sometimes it is known as China's {#blank#}2{#/blank#}( five) great invention. People can use the abacus {#blank#}3{#/blank#} (calculate) at a faster speed, so it has been called"the {#blank#}4{#/blank#}( old) computer in the world".

 To use the abacus correctly, something {#blank#}5{#/blank#} ( be) necessary for you to know. It usually has more than seven rods(杆子). There are two beads(算珠) on each rod in the upper deck(层) and five beads each in the bottom. The beads are usually round and made {#blank#}6{#/blank#} wood. We count the beads by {#blank#}7{#/blank#}( move) them up or down towards the beam (横梁). If you move them towards the beam, you count their value. {#blank#}8{#/blank#}, if you move them away the beam, you can't count their value. The_abacus can be reset(重置) to the starting position quickly, so you can start to count again {#blank#}9{#/blank#}(easy). Today, the use of abacus is still taught in some primary  {#blank#}10{#/blank#} ( school) as part of maths.