题目

赫尔希和蔡斯的T2噬菌体侵染细菌实验表明了A. 病毒中有DNA，没有蛋白质 B. 细菌中有DNA，没有蛋白质C. 蛋白质和DNA，是遗传物质 D. DNA是遗传物质 答案：【答案】D【解析】试题赫尔希和蔡斯的T2噬菌体侵染细菌实验表明了噬菌体的DNA是遗传物质，由于蛋白质没有进入到细菌中，因此该实验不能证明蛋白质不是遗传物质，故D正确。Dear Mr. Black，I’m very thank to you for inviting me to stay with you in the come summer vacation. I have been dreamed of seeing you again so that I can get help from you in my English learning. And I’m afraid I cannot go to your place in this summer. I’ve promised my grandmother, she lives in the country, to spend this summer with her. She misses me too much that I find difficult to refuse her request. I’m busy preparing for my examinations in present. I planned to visit you in winter if it’s convenient to you.Best wishes.Yours truly,Li Ying