题目

The New York Times, the Wall Street Journal, Financial Times and some other newspapers have published articles indicating that cyber attacks targeting Google and several other U．S．companies were from China．Such accusations are biased（有偏见的）． These articles take as evidence that hackers’ IP addresses could be traced back to two schools in China．However, it is common sense that hackers can attack by controlling computers from anywhere in the world．This fact also explains why hackers are hard to be tracked down． Computers in China are easy to be controlled by hackers as肺炎双球菌转化实验中，在A、B、C、D四个试管中都培养有R型细菌，然后在四只试管中分别加入从S型活细菌中提取的蛋白质、DNA＋DNA酶（能水解DNA）、DNA、多糖，经过一段时间的培养，能检查出S型活菌的试管是：