作业帮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 alkalin
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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 alkalin
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
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 alkalin
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.
BBAC
BBAC