答案：B

题目分析：句意：——约翰，你好。怎么啦？——是我的狗，露西，她的腿受伤了。A. How are you   你好；B. What's the matter  怎么啦； C. Who's that 那是;   D. What's Lucy like露西怎么样；根据Her leg is hurt.可知此处出现了问题，故问她怎么啦。故选B。