题目

下列关于艾弗里的肺炎双球菌转化实验的叙述中,错误的是( )A. 需对S型细菌中的物质进行提取、分离和鉴定B. 配制培养基的成分应适合肺炎双球菌的生长和繁殖C. 转化的有效性与R型细菌的DNA纯度密切相关D. 实验证明了DNA是遗传物质而蛋白质不是遗传物质 答案：【答案】C【解析】需对S型细菌中的物质进行提取、分离和鉴定，以便进行确定转化因子是何种物质，A正确；配制的培养基应适合肺炎双球菌的生长和繁殖，以确保肺炎双球菌能增殖和转化，B正确；转化的有效性与S型细菌的DNA纯度有密切关系，C错误；艾弗里将S型细菌的各种成分分离开，分别于R型细"Eyes are windows of the soul." Everyone knows the 36 of the eyes.  37 more and more students are becoming near-sighted(近视). So how to protect the eyes is still a serious problem. Here is some advice on 38 protect your eyesight(视力). You should not keep your eyes 39 for a long time. When reading, you should keep the books about a foot away from you. After reading for an hour 40 two, you 'd better have a 41 by looking into the distance(远处). You must remember not to read in dark light or in 42, not to read on a moving bus or in bed. Doing eye exercises will help 43 to protect your eyesight. In a 44  , to keep 45 eyesight, we must have good studying habits. 36. A. importance B. experience C. difference 37. A. So B. Because C. But 38. A. what to B. how to C. when to 39. A. working B. walking C. waking 40. A. and B. or C. as 41. A. talk B. rest C. by 42. A. the earth B. the star C. the sun 43. A. him B. us C. you 44. A. word B. sentence C. letter 45. A. bad B. good C. weak