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【单选题】
PM2.5是指悬浮在空气中,空气动力学当量直径≤( )的颗粒物。A.
2.5μm
B.
2.5mm
C.
2.5cm
D.
2.5nm
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举一反三
【单选题】The reason ___ the bus was late is there was an accident just now.
A.
why
B.
when
C.
where
D.
which
【单选题】机场控制区应当根据( )的需要,划定为候机隔离区、行李分检装卸区、航空器活动区和维修区、货物存放区等,并分别设置安全防护设施和明显标志。
A.
保证安全
B.
正当防卫
C.
安全保卫
D.
安全防护
【简答题】There is an old story telling about a woman whose only son died in an accident. In her 26 , she went to the wise man that is always 27 for his wisdom in her town and said, “What advice or what 28 ways...
【简答题】We left in such a hurry that we forgot to lock the door.
【简答题】如图所示，三相异步电动机的机械特性与恒转矩负载的机械特性(转矩大小不随转速变化)交于A、B两点(T L 等于额定电磁转矩T N )，与风机负载的机械特性(转矩近似与转速的平方成正比)交于C点。不计空载转矩，试问：在A、B、C三点中，电动机能在哪些点稳定运行?能在哪些点长期稳定运行?
【简答题】They feel that it is only a matter of time before there is an accident as a lot of the children walk to the school.
【单选题】—Why is the classroom so dirty? —Sorry，sir. It yesterday, We forgot to do it.
A.
doesn’t clean
B.
didn’t clean
C.
isn’t cleaned
D.
wasn’t cleaned
【单选题】与固有机械特性相比，人为机械特性上的最大电磁转矩减小，临界转差率没变，则该人为机械特性是三相异步电动机的（ ）。
A.
降低电压的人为机械特性
B.
定子串接电阻的人为机械特性
C.
转子串接电阻的人为机械特性
D.
改变频率的人为机械特性
【单选题】It is reported______there was an accident in town yesterday.
A.
where
B.
which
C.
here
D.
that
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