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阅读下面短文，从短文后每小题的四个选项中选出能填入相应空白处的最佳选项。

    Everyone knows water is important to all living things. But do you know these interesting 1 about water?

    Without water, the Earth would look 2 the moon. People can live several days without food, but only3days without water. Scientists say 70% of the human body is made up of water. Water 4 up 83% of our blood, 70% of our brain, and 90% of our lungs (肺). About 95% of a tomato is water, and about 80% of an apple is water. So 5 can we do to help with water problems?

   Keep a shower to 10 minutes or 6 time. It helps save much water. Use a broom to sweep the floor, the stair, the garage (车库), or the sidewalk instead of water.

     7 throw your used water away. Instead, you can use some to water plants or run the toilets. Use a bucket (桶) of water to 8 your bike or the  family car instead of water pipes.

     Use water only 9 you need it. Don't leave water running. Be sure to turn the tap 10 when you are not using it.

 $\sqrt{{\left(-4\right)}^2}$=____ ．

反应：2A(g)＋B(g)2C(g)，当平衡向正方向移动时，下列说法一定正确的是