题目

The little boy came riding full speed down the motorway on his bicycle. ______ it was!    A. What a dangerous scene      B. What dangerous a scene    C. How a dangerous scene       D. How dangerous the scene 答案：A 解析: 感叹句句型。英语中的感叹句分what和how开头两种：1）What +a/an+形容词+单数可数名词+主语+谓语；What+形容词+不可数名词（复数名词）+主语+谓语  2）How+形容词（副词）+主语+谓语；How+形容词+a/an+单数可数名词+主语+谓语根据以上结构，四个选项只有A项正确。x+y=3，xy=-4，则xy3+x3y=______．