第6题: [单项选择]Questions 22-25 are based on the following passage.What is in great demand in factories A. Diamonds. B. Diamond dust. C. Big diamond stones. D. Hard steel. 参考答案:B 答案解析:本题的关键词句为it is not the big stones needed for the drills,和demand the diamond dust…由关键词可推断出答案。