如果声称一种食品“无或不含糖”,是指这种食品中绝对不含糖。
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以下哪个不是抽样估计中估计量的评选标准( ).
A. 无偏性
B. 有效性
C. 相合性
D. 充分性
比较参数的两个估计量的有效性时,必须保证它们是无偏估计量.
A. 对
B. 错
In the lobby, I noticed a foreigner ____________something to an attendant.
A. explains
B. explaining
C. explained
D. to explain
It seemed that the attendant and the foreigner _________ understand each other.
A. couldn't
B. can't
C. mustn't
D. needn't
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