第25题: [单项选择]He had already walked three or four miles ______ he saw a cart, half-full of hay, by the side of the road. A. while B. when C. the moment D. unless 参考答案:B 答案解析:[考点] when的用法
[解析] when“这时(突然)”。常见的搭配有:be doing…when…;be about to do…when…;had done…when…。例如:I wa