题目

_____ troubles me is _____ I don’t know _____ is to be done with the new machine.A. What; what; that                         B. What; that; how  C. What; that; what                         D. What; because; which 答案：C一件大衣420元，买一件大衣的钱可以买3件毛衣．一件毛衣比一件大衣便宜多少元？