The professor walked onto the platform and seated himself in a chair for answering quest

问题补充：

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

答案：

A. had prepared

B. being prepared

C. preparing

D. prepared

解析：本题主要考查对句子结构的理解。根据句子中的walked onto…and seated himself…可知，句子表示几个动作的延续，应该用几个动词的并列答案选D。