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

问题补充：

The principal walked onto the platform and seated himself in a chair, for answering questions.

A. prepared

B. being prepared

C. prepared

D. preparing

答案：

A. prepared

B. being prepared

(答案→)C. prepared

D. preparing

解析：此处prepared相当于形容词，意为：准备好了的。这里形容词短语作伴随状语。故选C。句意：校长走上讲台，坐下，准备回答问题。