请将下面作文中划线的句子改为被动语态，体会一下被动句的妙用。

　　①People generally believe that there is a good supply of fresh water．To our disappointment, the fact is just the opposite．

　　As we can see, the world population is growing rapidly day by day．②So we need enough fresh water to feed such a big population．What's more, with the development of industry, factories and vehicles produce poisonous gases or wastes, which consequently results in the pollution of water．③Though the water looks fresh, we can no longer use a good amount of it．Only quite limited fresh water resource is available to human beings．So it's high time for us human beings to take quick action to protect water resource．Stop pollution and save water, otherwise, we cannot survive on the earth．

观察下列句子中的画线部分，归纳出各种时态的被动语态的构成。

1．Rice is grown in the south of China．

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2．The computer is being used now．

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3．The work has been finished．

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4．The thief was caught yesterday．

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5．The girl was being operated on in the hospital．

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