Pool experts have determinded the proper levels of chemicals

来源：学生作业帮编辑：灵鹊做题网作业帮分类：英语作业时间：2024/04/28 16:21:50

Pool experts have determinded the proper levels of chemicals that must-------in pool water to protect the swimmers from infection and the equipment-------corrosion and damage.Chlorine keills harmful organisms,but it won't work properly if the alkalinty of the water is too----.If the calcium content of the water is inadequate,the water will leach calcium from the walls of the pool,------them
1.A.maintain B.be maintained C.have maintained D.be maintaning
2.A.by B,from C.for D.of
3.A.low B.below C.under D.beneath
4.A.have weakened B.is weakening C.weakening D.weakens

1.选B.这里是一般的情况.maitain维持,保持.游泳池中的学药品的含量必须保持在一个恰当的水平.在这里要用被动语态,是人类保持其含量.
2.选B.and the equipment-------corrosion and damage与前一短语to protect the swimmers from infection 结构是一样的,只不过是省略了一些相同的词而已.
3.选A.如果水中碱的浓度太低,它就不起作用了.
4.选C.表示伴随动作.

Pool experts have determinded the proper levels of chemicals Experts have been warning ---of the risks caused by passive 翻译:we know that the levels of carbon dioxide have increased Sea levels have been rising ____ the beginning of this centu Experts have been warning ---of the helth risks caused by pa Experts have been warning of the health risks caused by pass 英语翻译82、Experts have been warning for some time of the health the trigger chemicals中of+the+名词的用法! pool deck Some of the best views of any city I have seen hav 英语翻译The 'List of Approved Chemicals with Corresponding Brand people are concerned that the persistence of high levels of we swim in the ___(swim)pool.we have a lot of things___(pack