根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

　　1. It is a new term in today's tourism industry．But in an age of growing environmental awareness, it is not too difficult for us to imagine and understand this new form of holiday．

　　Ecotourism, which is considered as a kind of responsible tourism, is typically defined（定义）as travel to places where special and unusual plants, animals and cultural heritages （遗产） are the main ttractions．  2. Therefore, programs concerning the protection of some natural and cultural spots also form'a part of ecotourism．　　Ecotourism is developing at great speed．According to a recent report by the World Tourism Organization, ecotourism in recent years has enjoyed an annual growth of about 5% worldwide． 3.  They include bird watching, hiking, diving, photography and taking part in various kinds of local cultural events．　　4.  However, it looks like some smaller towns and country areas may well become the new destinations for people to visit tomorrow because they are rich in ecological, cultural and historical resources （资源）．

　　Ecotourism has been gaining increasing recognition and popularity mainly for the relaxing, natural and vivid experience it offers to tourists．People are attracted to nature  and long to be close to it．However, a conflict between nature and human beings is unavoidable． 5.

　　A．The definition of ecotourism is beyond words．

　　B．It takes ecology and culture into consideration．

　　C．You may not be very familiar with "ecotourism"．

　　D．More than 80 activities have been listed for ecotourism．

　　E．People can have great fun enjoying nature through ecotourism．

　　F．Big cities are still the major places that attract tourists in our society today．

　　G．How to protect natural resources while taking advantage of them is of great importance．

It is natural that children are curious (好奇的) about the world around them. For example, they want to know how their hearts beat. They want to know why the ocean water tastes salty.

　　As children grow up, they become curious about different kinds of things. When they are babies, they are interested in the parts of their bodies and in the smiles of their mothers. They become interested in the physical world around them: the plants, the animals, the sky. Later, they become interested in the things that people have made: wheels, bicycles, cars. And when they are adults, their curiosity continues. Sometimes this curiosity leads to a career (生涯、职业) in science.

　　Scientists spend their lives trying to find out about the world. Those who work with the earth sciences study the earth, the oceans, and the skies. Other scientists who study living things work with the biological sciences. A third group of scientists study the physical sciences, e. g. physics, chemistry .

　　These scientists have already discovered a lot about our world. For example, they tell us why your heart beats fast when you run. They say that when you are quiet, your heart normally beats sixty-five or seventy-five times a minute. Your heart is a pump (泵) that pumps blood to all parts of the body. The blood carries oxygen and nutrition. When you run, your muscles work very hard and use the nutrition that the blood carries to them. The muscles need oxygen, too . So your brain sends a signal to the heart. The signal means that the muscles need more nutrition and oxygen. Then the heart beats fast and sends blood quickly to the muscles. It may beat 90 to 140 times a minute.

　　Of course, scientists cannot answer all of our questions. If we ask, “Why does the ocean water taste salty” scientists will say that the salt comes from rocks. When a rock gets very hot or very cold, it cracks. Rain falls into cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt into the ocean. But then we ask , “What happens to the salt in the ocean? The ocean does not get saltier every year.” Scientists are not sure about the answer to this question.

　　We know a lot about our world, but there are still many answers that we do not have, and we are curious.

According to the passage, which of the following statements is true?

　 A．People are curious in the same way.

　 B．People in different countries are interested in different things.

　 C．Men and women are curious about different things.

　 D．People of different ages are interested in different things

Scientists who work with the biological sciences study____.

    A．the earth , the oceans and the sky   B．man-made things

    C．plants and animals   D．ocean water

When you run, your muscles need ____.

A．more nutrition and oxygen    B．more signals   

C．more salt                  D．water

A rock cracks _____.

A．in wet regions       B．in dry regions

C．at very high or very low temperatures     D．when salty water falls in

People are always curious because ____.

A．they cannot explain many things  B．they know nothing about the world

C．they know little about the world  D．they want to be scientists