The water we drink and use is running short in the world.We all have to learn how to stop wasting our limited water.One of the steps we should take is to find ways of reusing it.Experiments have already been done in this field. Today in most large cities,fresh water is used only once,then it runs into waste system.But it is possible to pipe the used water to a purifying factory.There it can be filtered and treated with chemicals so that it can be used again,just as it were fresh from a spring. But even if every large city purified and reused its water,we still would not have enough.Then we could turn to the oceans.All we’d have to do to make use of the seawater on earth is to get rid of the salt.This process is called desalinization,and it is already in use in many parts of the world. The way to stop wasting our limited water is to________.

材料题

glass of water for every 20 minutes you are active.If you drink coffee or alcohol,you should add at least an equal amount of water.When you are traveling on an airpiane,it is good to have 8 ounces of water for every hour you are on board the plane.4 It may be difficult to drink enough water on a busy day.Be sure you have water handy at all times by keeping a bottle for water with you when you are working,traveling,or exercising.If you get bored with plain water,add a bit of lemon for a touch of

答案解析

单选题

The water we drink and use is running short in the world.We all have to learn how to stop wasting our limited water.One of the steps we should take is to find ways of reusing it.Experiments have already been done in this field.Today in most large cities,fresh water is used only once,then it runs into waste system.But it is possible to pipe the used water to a purifying factory.There it can be filtered and treated with chemicals so that it can be used again,just as it were fresh from a spring.Bu

答案解析

材料题

glass of water for every 20 minutes you are active.If you drink coffee or alcohol,you should add at least an equal amount of water.When you are traveling on an airpiane,it is good to have 8 ounces of water for every hour you are on board the plane.4 It may be difficult to drink enough water on a busy day.Be sure you have water handy at all times by keeping a bottle for water with you when you are working,traveling,or exercising.If you get bored with plain water,add a bit of lemon for a touch of

答案解析

材料题

glass of water for every 20 minutes you are active.If you drink coffee or alcohol,you should add at least an equal amount of water.When you are traveling on an airpiane,it is good to have 8 ounces of water for every hour you are on board the plane.4 It may be difficult to drink enough water on a busy day.Be sure you have water handy at all times by keeping a bottle for water with you when you are working,traveling,or exercising.If you get bored with plain water,add a bit of lemon for a touch of

答案解析

单选题

Eventhing we eat and drink contains some salt; we can meet the body’s need for it from natural sources without turning （） the salt bottle .

答案解析