单选题 Diamonds that are flawed or are too small for jewelry are used to cut very hard metals.
A. tiny B. imperfect C. luminous D. crude

【正确答案】 B
【答案解析】[解析] 划线词are flawed“有缺陷的”。A项tiny“微小的”；B项imperfect“有缺点的”；C项luminous“发光的，明亮的”；D项crude“天然的”。显然，B项与之语意符合。