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【单选题】
使用二氧化碳灭火器时,要注意窒息性气体的浓度,空气中二氧化碳含量达到( )会使人呼吸困难。.............................................................................................( )A.
5%
B.
8.5%
C.
10%
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举一反三
【单选题】在探究鼠妇生活环境的实验中,老师提出“为什么在花盆下、石块下等处容易找到鼠妇?”有的学生猜测可能鼠妇的活动与光照条件有关,有的学生猜测鼠妇的活动可能与水分有关 等,这个过程属于探究过程中的
A.
提出问题
B.
做出假设
C.
设计方案
D.
实施方案
【单选题】In the squirrel-cage motor, the speed of the rotor is _______ than the speed of the magnetic field.
A.
greater
B.
less
【简答题】将抗生素注入人体会产生抗生素与血浆蛋白质结合的现象,以致减少药效。现将 5 中常用的抗生素注入牛的体内,得到抗生素与血浆蛋白质结合的百分比如表 : 进行 的统计结果:统计量 = ,P = ,根据检验水准, (接受或拒绝)原假设,结论: 这5种抗生素引起的抗生素与血浆蛋白结合的百分比 (有或无)显著差异。 (注:1.保留小数点后三位,2.统计方法选择有:单个样本均值t检验、配对设计样本t检验、两个独...
【单选题】The ______ cage rotor induction motor is the first choice marine motor in most modem ships because of its electrical and mechanical simplicity.
A.
single phase
B.
two phase
C.
three phase
D.
four phase
【单选题】The rotor of a squirrel-cage motor is constituted by a system of bars, which are _____ by two rings located on the extremities.
A.
open in short-circuit
B.
closed in short-circuit
C.
closed in break-circuit
D.
open in break-circuit
【单选题】The ___ , cage rotor induction motor is the first choice of marine motor in most modern ships because of its electrical and mechanical simplicity.
A.
single phase
B.
two phase
C.
three phase
D.
four phase
【单选题】The ____, cage rotor induction motor is the first choice marine motor in most modern ships because of its electrical and mechanical simplicity.
A.
two phase
B.
three phase
C.
single phase
D.
four phase
【判断题】In squirrel cage induction machine, the rotor winding is short circuited.
A.
正确
B.
错误
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