几个有理数相乘，下列结论正确的是（） A．负因数有奇数个

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问题选择题

几个有理数相乘，下列结论正确的是（　　）

A．负因数有奇数个时，积为负

B．负因数有偶数个时，积为正

C．积为负数时，负因数有奇数个

D．因数有偶数个时，积为正

答案

答案：C

填空题

根据中文提示完成下列短文。

It was Saturday. John (游泳) in the sea. Wu Yifan (踢足球) with his friends. Chen Jie

wasn't at school, she (读书) at home. Mike (去远足) with his parents. Zhang Peng

(去滑冰) with his father. Liu Yun (洗衣服) in the bathroom. They all had fun.

多项选择题

超短波通信信道影响因素有（）。

A.工作频率

B.通信距离

C.地形

D.气象