题目

Wait a few minutes and I have to have a look, for I                 (闻到什么在烧) 。( smell) 答案： smell/ have smelt something burning   下列运算正确的是（　　） A、3a+2a=5a2B、a2•a3=a6C、（a+b）2=a2+2ab+b2D、（x+y）（x-2y）=x2-2y2