问题
单项选择题
基因突变在生物进化中起重要作用，下列表述错误的是（）
A.A基因突变为a基因，a基因还可能再突变为A基因
B.A基因可突变为A1、A2、A3……，它们为一组复等位基因
C.基因突变大部分是有害的
D.基因突变可以改变种群的基因频率
答案
参考答案：C
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基因突变在生物进化中起重要作用，下列表述错误的是（）
A.A基因突变为a基因，a基因还可能再突变为A基因
B.A基因可突变为A1、A2、A3……，它们为一组复等位基因
C.基因突变大部分是有害的
D.基因突变可以改变种群的基因频率
参考答案：C
I went back to China as soon as school was over at the end of June. And I returned to Canada on August 17th. It’s to go back to China this summer, because of the A（H1N1）flu. Everybody seemed to be . The easiest thing for us to do was to wear masks（口罩）on the plane, as my mom suggested. However, it was not to wear a mask for ten hours. I decided to put the masks into my bag wearing them. Everything seemed OK the flight. I saw only five people wear masks all the time. When we arrived in Beijing, some came into the plane and took our temperature. Fortunately, had a fever. Therefore, I was able to get home on time. However, everything went wrong after I got home. I became sick, with a sore throat and a fever because I had not my mom’s words. Luckily, I just had a common . while I was sick in bed, I thought that if I had listened to my mom at first, I would have never caught the cold. It’s always wise to listen to your mom’s suggestions.
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