下列图示可以正确表示染色体、DNA、基因三者之间关系的是（ ）
A．
B．
C．
D．
染色体是细胞核中容易被碱性染料染成深色的物质，染色体是由DNA和蛋白质两种物质组成；DNA是遗传信息的载体，主要存在于细胞核中，DNA分子为双螺旋结构，像螺旋形的梯子；DNA上决定生物性状的小单位，叫基因．基因决定生物的性状．一条染色体有一个DNA分子组成，一个DNA分子上有许多个基因．因此基因位于DNA上，DNA位于染色体上．即：
．
故选：C．
| 根据对话内容从方框内所给的选项中选出最佳答案，使对话完整,符合逻辑，句意通顺，注意有多余选项。 | |
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| A: You must be really excited about leaving for America tomorrow, Li Ping! B: Yeah. 1 A: Nervous about what? B: I don't know many of the customs and manners in the USA. 2 A: Sure. B: 3 A: Well, it's important to be on time when you're invited for dinner. 4 Americans expect their guests to be on time. B: Then how long may I stay there? A: 5 Or you seem to have come only for the meal. When your friends seem to be getting tired and running out of things, it's time to leave. The next day, call or write a thank-you note to say how much you enjoyed the evening. |