题目

The boss____________ the worker how to do it, or the accident couldn't have happened. A. can't have told              B. ought to tell C. could have told              D. mustn't have told 答案：A 解析: 抓住关键“or”，意为“否则”，所以前后意思相反。2、下列从左到右的变形，是分解因式的是（　　）A、x（x-1）=x2-xB、x2+6x+8=（x+3）2-1C、a2-a-2=a（a-1）-2D、m2-1=（m+1）（m-1）