题干

在DNA复制的过程中,DNA分子首先利用细胞提供的能量,把两条螺旋的双链解开。这时需要用到的酶是

A:DNA连接酶

B:DNA酶

C:DNA解旋酶

D:DNA聚合酶

上一题 下一题 0.0难度 选择题 更新时间:2018-04-16 05:05:15

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四个选项(A、B、C、D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

    Walt Disney was born on December 5, 1901 in Chicago Illinois while he lived most of his childhood in Marceline, Missouri.

    Since young, Walt showed great 1 in art. He would often sell drawings to neighbors to make 2 money. Though his father could be quite 3, and often there was little money in the family, Walt was 4 by his mother, and older brother to 5 his attention on what he loved deeply.

    In 1918, Disney 6 to enter the army. However, he was 7 because he was under age, only 16 at the time. 8, Walt joined the Red Cross and was 9 to France, where he spent a year driving an ambulance(救护车).His ambulance was 10 not with army camouflage(伪装),but with Disney cartoons.

    Once Walt 11 from France to America, he started a small company which finally 12 to be a failure. With twenty dollars, Walt  13 for Hollywood to try his luck. After making a  14 of his “Alice Comedies”, Walt became a(an) 15 Hollywood figure. In 1932, Flowers and Trees(the first color cartoon) 16 Walt the first of his studio's Academy Awards. His dream of a clean, and organized amusement park  17 as Disneyland Park opened in 1955.

    Walt Disney is a hero of the 20th century. His worldwide popularity was 18 on the ideals(标准): imagination, creation and self-made success in the American 19. He brought us closer to the future 20 telling us of the past. It is certain that Walt Disney is a great man.

同类题3

完形填空

      A couple of weeks ago, I made a trip to Toronto with my granddaughter who just turned three years old. The two of us were on our way to  1   her parents, and my wife—her  2    who had been gone for over a week. We were all anxious to  3    again and as I pulled out of Mamere and Papere's driveway in Chelmsford, Hailee and I were both  4    about the trip and couldn't wait to arrive at our   5.

When we completed the “SEVEN”-hour trip to Toronto later that day, the reunion was absolutely  6 and I can sincerely say I enjoyed every single minute of that   7     journey.

      Hailee is at that “I want to  8  it myself” stage of her life. And if you can just get over the “hurry-up syndrome” we acquire as  9, it is wonderful to witness. Who knew that putting a straw into the  10  in a juice box for the very first time could be such an earth-shattering (惊天动地的) event? Or being  11  enough to actually open the fridge door for the first time? Or putting on your own  12  on the right feet would be so  13?

      I'll never forget the look on her face the day she was able to  14 into my truck by herself. She finally  15 on my seat, holding onto the steering wheel (方向盘) and declared 16, “I did it!” And when she could actually put her own seat belt on—what a(n)  17!

    Have you ever watched a three-year-old 18 to sip a McDonald's milkshake through a straw? It is hard enough for an adult, too. And 19 every time the icy solution (溶液) touched her lips, you could see the 20 in her eyes. I learned that you can't hurry a child through a milkshake.