David worked hard at his lessons he gained high grades in the exams.
A. so that
B. in order to
C. though
D. because
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(答案→)A. so that
B. in order to
C. though
D. because
解析：句意：David努力学习功课，以便在考试中取得更好的分数。so that以便，表目的。in order to+动词原形；though尽管；because因为。根据句意故选A。