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【单选题】
位于A,B两点的两个波源,振幅相等,频率都是100Hz,相位差是 ,其A,B相距30m,波速为400m/s,那么A,B连线之间因相干干涉而静止的各点的位置(与A的距离)不可能是()。A.
12m
B.
13m
C.
15m
D.
29m
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【简答题】许可证件管理系指一定时期内(一般是1年)，国家对部分商品的进口制定关税配额税率并规定该商品进口数量总额，在限额内，经国家批准后允许按照关税配额税率征税进口，如超出限额则按照配额外税率征税进口。( )
【单选题】What happened to the horse lover when he tried to slap the fly on his horse’s leg?
A.
By doing so, he frightened his horse and got killed by the horse
B.
By doing so, his horsed loved him more than ever
C.
By doing so he created a good environment for his horse.
D.
By doing so he startled the fly and the fly flied away
【单选题】Ted worked like a horse in his youth, ______ contributed to his great success later as a businessman.
A.
that
B.
who
C.
what
D.
which
【简答题】端口特性为 u=3q+4 的二端电路元件是 _______ 元件。 1) 电感 2) 电容 3) 电阻
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【单选题】进口配额管理是指国家在一定时期内(一般是1年)，国家对部分商品的进口制定配额优惠税率并规定该商品的进口数量总额，在限额内，经过国家批准后允许按照配额内的优惠税率征税进口，如超出限额则按照配额外的税率征税进口的措施。 ( )
A.
正确
B.
错误
【单选题】One day a poor man ____ his horse to a tree, and sat down to eat his lunch.
A.
closed
B.
tyed
C.
tied
D.
lied
【单选题】许可证件管理系指一定时期内(一般是1年)，国家对部分商品的进口制定关税配额税率并规定该商品进口数量总额，在限额内，经国家批准后允许按照关税配额税率征税进口，如超出限额则按照配额外税率征税进口。 ( )
A.
正确
B.
错误
【简答题】哪些方法可以减轻家电辐射的危害?
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