题目

用3、6、7 能组成________个不同的两位数，用2、0、5 可以组成________个不同的两位数。 答案：【答案】6 4 【解析】第一组：哪个数字都可以作为十位数字，列举出所有数字即可判断；第二组：0不能作为十位数字，列举出能组成的数字即可.用3、6、7组成的两位数：36、37、63、73、67、76共6个；用2、0、5组成的两位数：20、25、52、50共4个.故答案为：6；4Using too much water or throwing rubbish into our rivers are clear ways that humans can put our water supply in danger ,but we also affect our water supply in less obvious ways .You may wonder how paving(铺砌) a road can lead to less useable fresh water . A major part of the water we use every day is groundwater . Groundwater does not come from lakes or rivers .It came from underground . The more roads and parking lots we pave ,the less water can flow into the ground to become groundwater .Human activity is not responsible for all water shortages(短缺). Drier climates are of course more likely to have droughts(干旱) than areas with more rainfall ,but in any case, good management can help to make sure there is enough water to meet our basic needs .Thinking about the way we use water every day can make a big difference ,too. In the United States ,a family of four can use 1.5tons of water a day ! This shows how much we depend on water to live ,but there’s a lot we can do to lower the number .You can take steps to save water in your home .To start with ,use the same glass for your drinking water all day .Wash it only once a day .Run your dishwasher (洗碗机)only when it is full 。Help your parents fix any leaks in your home . You can even help to keep our water supply clean by recycling batteries instead of throwing them away .1..Which of the following is most likely to lead to less groundwater ?A. paving parking lots . B.Throwing batteries away .C. Using river water D. Throwing rubbish into lakes .2. What can be inferred from the text ?A. All water shortages are due to human behavior .B. There is much we can do to reduce family size .C. It takes a lot of effort to meet our water needs .D. The average family in America makes proper use of water .3.The last paragraph is intended to .A.show us how to fix leaks at homeB. tell us how to run a dishwasherC. prove what drinking glass is best for usD. suggest what we do to save water at home4.The text is mainly about .A. Why paving roads reduces our waterB. how much we depend on water to liveC. why droughts occur more in dry climatesD. how human activity affects our water supply