I believe it’s for the reason he had to drop out of school and left his hometown.
A. why
B. how
C. what
D. that
网友回答
A. why
B. how
C. what
(答案→)D. that
解析：考察强调句型。强调句型的基本结构为：It is/was 被强调部分that/who其他部分；去掉it is/was that/who仍然成立。句意：我认为正是因为那个原因，他才辍学并离开家乡的。