The little boy came riding full speed down the motorway on his bicycle, ________ it was!
A.What a dangerous sceneB.What dangerous a sceneC.How a dangerous sceneD.How dangerous the scene在线课程A
解析：
句意：这个小男孩骑着自行车全速地在高速公路上飞驰，多危险的一幕啊！感叹句是常用句式，结构为：What a/an+adj.+n.+主语+谓语！或How+adj.+a/an+n.+主语+谓语！根据句子结构，答案选A。此句也可说成：How dangerous a scene it was!