The professor walked onto the platform and seated himself in a chair, for answering questions.
A. had prepared
B. being prepared
C. preparing
D. prepared
网友回答
A. had prepared
B. being prepared
C. preparing
(答案→)D. prepared
解析：be prepared for=prepare for为……作准备,故B、C、D三项从语法上都合题,但B、C项表动作,D项表状态。由题意知,此处须用过去分词作状语,表示伴随状态。