-- Do you know why he left so early ?-- for the English test I guess.A. To studyB. StudyC

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：句意：你知道为什么她离开这么早吗？我猜是为了英语测试而努力学习去了。不定式To study表目的，根据句意，故选A.