Mr. Bob, as a manager for many years, found it hard to be an ordinary clerk again.A. hav

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(答案→)A. having worked
B. worked
C. to have worked
D. working
解析：考查现在分词的完成式做状语：句意：做经理很多年后，鲍勃先生发现很难做一个普通的职员了。根据句意，鲍勃先生是先做经理，然后才发现做秘书难的，当状语的动作发生在主句的动作之前，用现在分词的完成式做状语，选A。