阅读短文，然后根据内容回答问题。

　　Water is a kind of liquid．It has no taste or smell．Water is useful and is important to us．Why? We use water to water the plants．We use water to wash our face or to have a bath．We drink water or we will die…Not too long ago, there was a man called Jacques Cousteau．He loved the beautiful colors, and the beautiful fish in the sea．However, when he returned some years later, the colorful coral reefs were dead and grey because the factory near the sea poured waste water into the sea．Jacques Cousteau decided to tell people how important it was to save the environment under the sea．He started the“Cousteau Society”to help protect life in the sea．Now there are over 30000 members all over the world．Since water covers most of the earth, Cousteau knew that we should keep the sea clean．We should not litter the sea, and should clean up the dirty parts．As water is very important to our environment, he encouraged everyone to take part in protecting our lakes, rivers, sea and ocean．

　　There are still a few people who are not protecting the water now in the world．For example, some factories pour waste things into the rivers, lakes or into the sea nearby．The water there has become very dirty and we can't use them at all．Although there are seventy-five percent of water in the world, we can only use fresh water, that there is only a little．So we should use little water when we need to use it．For example, I do not use too much water when I am washing my face or having a bath…It is important for us to keep the water clean．You may ask yourself, have I ever poured or thrown dirty things into the water? If your answer is“No”, that means you have already helped to protect the environment．It is our duty to protect the environment．You may ask yourself again, have I ever helped to clean up the water? If your answer is“Yes”, that means that you have already done something useful to improve the water．If we use up all the water, it is difficult for us to get it from anywhere, including the universe．It is terrible to think that people are too thirsty to live! I believe, that if everyone helps to protect the water, the water must be protected．You do not want to“kill”your son or your grandson, do you? So now let us to protect the water! Please don't let the last drop of water on the earth is we human's tear!

1．In the first sentence, what does the word“liquid”mean?

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2．Why were the colorful coral reefs dead and grey when Jacques Cousteau returned some years later?

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3．How can we keep the sea clean?

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4．How much fresh water have we got?

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5．What did Jacques Cousteau encourage people to do?

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