题干

对于下列式子,正确的说法有(   )

①表示DNA复制过程;   ②表示DNA转录过程; ③式中共有5种碱基;④式中共有8种核苷酸  ⑤式中共5种核苷酸  ⑥式中的A均代表同一种核苷酸

A:①②③

B:②⑤⑥

C:②③④

D:①③⑤

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答案(点此获取答案解析)

C

同类题4

阅读理解

    A year ago, I paid no attention to English idioms, though my teacher emphasized (强调) the importance again and again. But soon, the importance of English idioms was shown in an amusing experience.

    One day, I happened to meet an Englishman on the road, and soon we began to talk. As I was talking about how I was studying English, the foreigner seemed to be astonished. Gently shaking his head, shrugging his shoulders, he said, “You don't say!” “You don't say!” I was puzzled. I thought, perhaps this is not an appropriate topic (适当的话题). “Well, I'd better change the topic.” So I said to him. “Well, shall we talk about the Great Wall? By the way, have you ever been there?” “Certainly, everyone back home will laugh at me if I leave China without seeing it. It was magnificent.” He was deep in thought when I began to talk like a tourist guide. “The Great Wall is one of the wonders in the world. We are very proud of it..” Soon I was interrupted again by his words: “You don't say!” I couldn't help asking, "Why do you ask me not to talk about it?" "Well, I didn't request you to do so, " he answered, greatly surprised. I said, "Didn't you say' you don't say?”Hearing this, the Englishman laughed to tears. He began to explain, “'You don't say' actually means 'really!' It is an expression of surprise. Perhaps you don't pay attention to English idioms.” Only then did I know I had made a fool of myself. Since then I have been more careful with idiomatic expressions. Remember: what the English teachers said is always right to us students.