答案：B

题目分析：考查非谓语动词，名词the patient和动词treat是动宾关系，所以用过去分词作状语，所以选B

点评：本题重在理解非谓语动词的用法，非谓语动词是高考语法点的重中之重。把握好以下的知识：to do 表目的、将来；doing 表主动、伴随；done表被动、完成。同时答题步骤为：1.判断是否为非谓语动词，看是否有连词。2.找逻辑主语。3.判断逻辑主语与非谓语动词的关系。4.看是否非谓语动词动作发生在主句谓语动作之前，如果是之前，就用完成式的形式。

即学即练：_____ of danger in the street at night, she had to go home, with a friend ____ her.

A. Warning, following                B. Having warned, following

C. Having been warned, following      D. Warned, followed

选C