— Do you know why he left so early?—for the English test I guess.A. To study B. Study C.

问题补充：

— Do you know why he left so early?

—for the English test, I guess.

A. To study

B. Study

C. Studied

D. Studying

答案：

(答案→)A. To study

B. Study

C. Studied

D. Studying

解析：非谓语动词的用法。根据句意“你知道他为什么离开那么早吗？”“我猜是为了英语考试。”，表示目的，用动词不定式，故选A。