题目

根据概念图，下列叙述正确的是( )A. A表示的碱基有5种 B. B表示的是核糖C. D表示的脱氧核苷酸 D. E表示脱氧核糖核苷酸 答案：【答案】C【解析】A是含氮碱基，组成DNA的碱基有4种，即A、C、G、T，A错误；组成DNA的五碳糖是脱氧核糖，因此B是脱氧核糖，B错误；组成DNA的基本单位是脱氧核糖核苷酸，因此D是脱氧核糖核苷酸，C正确；E是DNA，即脱氧核糖核酸，D 错误。比较项目 核酸 DNA RNA 基本单位 核苷酸 4种脱氧核苷酸 4种核糖核We all know that food makes us grow every day, but sometimes it can make us happy when we feel bad. Food such as sea fish, bananas, pumpkins and chicken can help us be happy. How can they affect (影响)our feelings?People living by the sea look much happier than other people, because the fresh sea air helps them clear their minds and they eat a lot of sea fish. Bananas have much Vitamin B6. Having more bananas can help us make a quick decision, and become more confident (自信). Eating pumpkins can also help people get into a good feeling because it’s rich in Vitamin B6 and iron (铁).Are you in a bad mood (情绪)? If you are, don’t sit alone. Go to eat such happy food with your friends. Maybe you’ll feel better.根据短文内容，判断下列句子正误。正确的用“A”表示，不正确的用“B”表示。【1】Food gives us energy and sometimes it can make us feel sad.【2】People living by the sea look happier because they have fresh air and eat sea fish.【3】Apples can make us more confident.【4】Eating pumpkins can help us get into a good feeling.【5】Vitamin B6 and iron can make us happier.