题目

下列关于遗传学经典实验的叙述中，正确的是（ ）。A. 艾弗里进行的肺炎双球菌体外转化实验证明DNA是遗传物质，蛋白质不是遗传物质B. 孟德尔通过豌豆杂交实验，提出一对同源染色体上的等位基因符合基因的分离定律C. 萨顿通过类比推理提出基因位于染色体上，并通过果蝇杂交实验证明了该假说D. 赫尔希和蔡斯在掌握了T2噬菌体侵染肺炎双球菌过程后用同位素示踪技术证明了DNA是遗传物质 Directions: Complete the following passage by filling in each blank with one word that best fits the context. Job hunting has always been a headache for college graduates. Though many graduates are employed right after graduation, some are   48 . Most serious of all, some still have no idea  49    to go working even a long time after graduation. The reasons   50  this phenomenon are various. On the one hand, a few years ago colleges and universities enrolled so many students in popular majors, such as economy, finance and so on   51    the number of graduates is greater than the need in the market. On the other hand, most graduates would rather stay in large cities without suitable jobs to do   52  go to the country. I believe the problem can be solved   53  both colleges and students take measures. First, they should research the market and develop special skills to suit   54  needs. Second, students’ attitude towards employment should be changed. They should go to some   55  cities and the countryside. There they can also give full play to their professional knowledge. In a word, if we pay much attention, the problem can be solved.