题干

下列关于核酸的叙述,正确的是(  )

A:核酸简称DNA

B:细胞生物都含有一种核酸

C:脱氧核糖核酸是细胞生物的遗传物质

D:组成核酸的基本单位是脱氧核糖核苷酸

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答案(点此获取答案解析)

C

同类题2

阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项。

    Gwondo was a trainer of dogs. He would go out every day with his dogs, to1 them how to catch animals so all his tribe(部落) could eat.

    Wherever Gwondo went, his tribe could see him away in the distance  2 his white hair would shine in the sunlight. The tribe 3would say to their children, "See, there is Gwondo and his dogs, searching for 4 for us all. " Gwondo went out hunting every day and always came 5 with much food. And all were very happy.

    Now Gwondo grew 6 and as all humans do, one day he died. The tribe felt sad and cried many days and many nights 7 one day the elders called to their children, " You have cried enough for Gwondo. Now it is time to 8 living. Go down to the beach and be happy."

    The children ran down to the beach and looked out to sea. 9, they all looked at each other, then turned and ran back to their elders, 10, "Come quickly. Gwondo, he is back with us. He is out in the sea. "The elders hurried to the 11 and said, "Yes! It is Gwondo back! He is now a dolphin and lives in the sea. "

    Now whenever you see 12 dolphins in the sea, look for the big old dolphin. You will know him because he has a large white fin on 13 back. He is Gwondo and he is training the young dolphins to chase(追逐) 14 close to the beach so that his tribe can catch them.

     Gwondo is known to all the tribes 15 the east coast of Australia. They call him their sea dog.

同类题5

完形填空

    One morning, the door to the classroom opened and a new teacher, Mrs Cosby, walked in. She looked too 1 to handle us. And we sure gave her a 2 time,but she never lost her temper. And then came the last day of the first month. She 3 a bunch of papers”. We4the worst—a test. But oh no, it was something that totally 5 us.

    Mrs Cosby asked us to come to the front of the class, and gave each of us a piece of 6, on which she had written what the student had been 7 at during the last month. You see, no one had ever 8 us. No one had ever liked us. We were constantly told what good - for - nothing Students we were. And here,9,was someone who had been 10 us closely for a month. We made things as difficult for her as we could. And yet she could find something 11 to say about each of us.

    Mrs Cosby did this every12 from then on. Each month we got a piece of paper that emphasized our 13 She commented on my courage, how punctual I was, how good to 14 arguements if I wanted. Her positive attitude transformed our class. We did not want to 15 her feelings anymore. We actually started to 16.

    And then came the day of our graduation. Mrs Cosby hugged us and told us with tears in her eyes how 17 she was of us. Then she 18each one of us a book. All the encouraging words through the years were there, in hard covers.

    She said, “I want you each to keep this book and if ever during your life you feel unworthy, 19this and read how good you are. You can be anything you want to be 20 you believe in yourself. Promise me you'll remember that!”