第12题: [单项选择]Which of the following did NOT cause so much trouble for the making of an atomic bomb.' A. Extraction of uranium. B. Sustentation of a reaction. C. Conversion from uranium ore to uranium metal. D. Separation of U-235 and U-238. 参考答案:B 答案解析:[题解] 根据提问,查看相关的段落,仔细辨别。选项B是分离铀的目的。而且应该是一系列的反应to sustain a chain reaction。