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举一反三
【单选题】高铁酸钾（K2FeO4）是一种高效的净水剂，下列关于该物质的叙述中正确的是（ ）
A.
它是一种氧化物
B.
高铁酸钾中铁元素的化合价为+6价
C.
它是一种混合物
D.
该物质含有两种非金属元素
【单选题】应用脱水剂时不正确的是（ ）。
A.
应在30分钟之内滴入
B.
20%甘露醇静脉滴注尽量快
C.
甘露醇有结晶，必须略加温后方可输注
D.
注意防止药液外渗
E.
必要时可重复使用
【单选题】Every year more than half a million American kids have drainage(排泄) tubes surgically implanted in their ears to combat persistent infections. The procedure, known as tympanostomy, may not be as (62) a...
A.
[A] feeling [C] health
B.
[B] hearing [D] memory
【单选题】Section BDirections: There are 2 passages in this section．Each passage is followed by some questions or unfinished statements．For each of them there are four choices marked A, B, C and D．You should de...
A.
could not easily be absorbed by the human body
B.
were potentially harmful to people's health
C.
were too expensive for daily consumption
D.
could not provide any cure for vitamin deficiencies
【单选题】下列关于掺防水剂水泥砂浆防水施工的说法中，错误的是()。
A.
防水砂浆中常用的防水剂有氯化物金属盐类防水剂和金属皂类防水剂
B.
当施工采用抹压法时，先在基层涂刷一层1：0.4的水泥浆，随后分层铺抹防水砂浆，每层厚度为10～15mm，总厚度不小于30mm
C.
氯化铁防水砂浆施工时，底层防水砂浆抹完12h后，抹压面层防水砂浆，其厚13mm分两遍抹压
D.
防水层施工时的环境温度为5～35℃