问题
单项选择题
组成核酸的基本单位是
A．含氮碱基
B．单核苷酸
C．多核苷酸
D．核糖核苷
E．脱氧核糖核苷
答案
参考答案：B
解析：核苷酸是核酸的基本组成单位，而核苷酸则包含碱基、戊糖和磷酸3种成分。答案选B。
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组成核酸的基本单位是
A．含氮碱基
B．单核苷酸
C．多核苷酸
D．核糖核苷
E．脱氧核糖核苷
参考答案：B
解析：核苷酸是核酸的基本组成单位，而核苷酸则包含碱基、戊糖和磷酸3种成分。答案选B。
At present, almost everyone has a mobile phone, but have you ever thought that cell phones be bad for your health? A study shows that heavy mobile phone use may cause hearing loss(失聪). This study shows that people who use cell phones for about an hour a day have a time hearing some similar sounds, especially in their right ears. It is getting harder for to tell the difference between the sounds of“s”and“f”，and“t”and“z”. Researchers studied 100 people who used cell phones and them with 50 people who did not. The study lasted for 12 months. What the researchers found was that cell phone users had more hearing than those who did not use cell phones. Besides this, our ears have many little inside them. Too much noise will cause these hairs to get weak and die. When these hairs die, it affects our ability to listen. However, cell phone users don’t care too much this study. One man said,“I’d be more worried about people who MP3 players. They put those earphones in their ears and listen to very music. I think that is more likely(更有可能的) to cause hearing loss than a cell phone.”
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