题干

下列有关科学家实验研究的叙述中,错误的是(   )

A:肺炎双球菌的体内转化实验肯定了转化因子的存在,但不能确定其化学本质

B:将R型活菌与S型菌的DNA与DNA水解酶混合培养,只生长R型菌,说明DNA被水解后,就失去遗传效应。

C:用含35S标记的噬菌体去感染普通的大肠杆菌,短时间保温,离心获得的上清液中的放射性很高,说明DNA是遗传物质。

D:用从烟草花叶病毒分离出的RNA侵染烟草,烟草出现病斑说明烟草花叶病毒的RNA可能是遗传物质

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答案(点此获取答案解析)

C

同类题2

      So far, there have been so many successful men and women in the world. And it's no surprise for many of us to dream of doing business when we grow up. However, Moziah Bridge tells us quite different story.

      Moziah Bridges is now the CEO of his Mo's Bow's company. He has already earned $200,000 by selling bow ties and other men's fashion accessories(饰品). The boy designs all the bow ties together with seven other workers in the company, including his mother and grandmother.

    “Mo is the CEO of the company, but I am the CEO of Mo,”Bridges' grandma said.

About four years ago, when Bridges went shopping for bow ties, he found they were in ugly" black and red. He wanted a change. So he asked his grandma to teach him to sew(缝纫)and finally he developed the talent of creating bow ties. Though his very first bow tie didn't look nice, the young sewer kept on practicing. He used colorful cloth with different pictures. Then his parents and friends started to like his works.

       At first he tried to sell them online to several stores in the south. Soon Mo's bow ties became popular. With the help of Dayond John, CEO of the famous US clothes brand FUBU, Bridges built his own company. Not only did Daymond John provide money for him, but also produced Bridges to the circle of fashion and business industries.

      Now the 13-year-old's business has developed rapidly. So you can just start now! You don't have to wait till you're older. If you have a dream, go for it!