There will be no giant pandas in the world if we ________ them．

A．doesn't protect                                 B．don't protect

C．didn't protect                                      D．wouldn't protect

Have you ever heard an echo of your voice?
An echo is a reflected(反射)sound. Stand in a very large, empty hall with nothing on the walls. Then shout. The sounds you make will hit the walls and come back to you. The walls reflect the sounds. These reflected sounds are called “echoes”.
We can use reflected sound to make sound travel farther. Hold a watch about fifty centimeters from your ear. You cannot hear it. The sound of the watch travels a short way in all directions. It does not travel as far as your ear. You can make it travel to your ear by using a roll of cardboard(纸板筒).
Make the roll of cardboard about fifty centimeters long. Put one end over your ear and hold the watch at the other. Now you can hear the watch because the sound has not gone in all directions. It is reflected down the roll to your ear.
A megaphone(喇叭筒)works in the same way. It makes sound travel farther. It reflects the sound into a beam which can travel a long way. In the ship, the sailor uses the megaphone to make his voice travel. Without the megaphone, his voice cannot travel far.
We use reflected sound in many ways. We use it to measure the depth of the sea, for example. Among the animals, bats and whales use reflected sound to tell them where they are and what things are near them.
【小题1】What is called “echo”?

阅读短文，从方框中选择适当的句子还原到短文中，使短文意思完整．
Scientists think that many or most animals can't see colors．【小题1】 ．To find out if dogs could see colors，scientists gave dogs food every time they played certain piece of music．  【小题2】 only when they heard this piece of music．They did not get ready to eat when they heard other pieces of music．
Then the scientists gave the dogs food every time they showed them a certain color．The dogs got ready to eat when they saw thi s color． 【小题3】 ．Again the dogs got ready to eat．The colors were al l the same to them．  【小题4】 ，however．For example if  we put food in a red box and do this every day．A monkey wiIi always go to the red box to get the food．  【小题5】 if we then put food in a blue box．

In the world today, all of the people need recreation（消遣）. We can not work all the time if we are going to keep healthy and enjoy life.
Everyone has his own way of relaxing. Perhaps the most popular form is to take part in sports. There are team sports, such as basketball and football. There are also individual（个人的） sports, such as swimming and running. Skating and mountain climbing are the most popular recreation for people who like to be outdoor（室外的）.
Not everyone who enjoys sports likes to take part in them. Many people like watching them on TV or listening to them on the radio. So many people like some forms of indoor recreation, such as watching TV, singing and dancing.
It doesn’t matter whether we like indoor recreation or take part in outdoor sports. It is important for everyone to relax from time to time, and enjoy some forms of recreation.
【小题1】 Which is the most popular form of recreation?

It can be hard to meet people from another culture. From the beginning, people may send the wrong signal (信号). Or they may pay no attention to signals from another person who is trying to develop a relationship.
Different cultures emphasize（强调）the importance of relationship building to a greater or lesser degree. For example, business in some countries is not possible until there is a relationship of trust. Even with people at work, it is necessary to spend a lot of time in “small talk”, usually over a glass of tea, before they do any job. In many European countries—like the UK or France—people find it easier to build up a lasting working relationship at restaurants rather than at the office.
Talk and silence may also be different in some cultures. I once made a speech in Thailand. I had expected my speech to be a success and start a lively discussion; instead there was an uncomfortable silence. The people just looked at me all the time and smiled. After getting to know their ways better, I realized that they thought I was talking too much. In my own culture, we express meaning mainly through words, but people there sometimes feel too many words are not needed.
Even within Northern Europe, cultural differences can cause serious problems. Certainly, English and German cultures share almost the same values; however, Germans prefer to get down to business more quickly. We think that they are rude. In fact, this is just because one culture starts discussions and makes decisions more quickly.
People from different parts of the world have different values, and sometimes these values are quite against each other. However, if we can understand them better, a multicultural (多元文化) environment will offer a wonderful chance for us to learn from each other.
【小题1】In some countries, eating together at restaurants may make it easier for people to   .