Ⅰ.甲磺酸乙酯(EMs)能使DNA序列中G﹣c碱基对转换成A﹣T碱基对.育种专家为获得更多的变异水稻亲本类型,常先将水稻种子用EMS溶液浸泡,再在大田种植,通常可获得株高、穗形、叶色等性状变异的多种植株.
Dear Editor,(编辑) I am unhappy these days. I am a student in Grade 3 of a middle school. I want to be a policewoman in the future. (未来) But my mother doesn't like the job. She always says it is too dangerous for a girl to work as a policewoman. She thinks girls should work in the office. She hopes that I can work as a doctor. But I really dislike being a doctor. It's terrible for me to work in the hospital. When I talk with her about it, she is often angry. She always thinks she is right. I don't know what to do. Can you help me? Yours, Nancy
一共有多少只小鸟?
世界上最高的大高原是( )