Why does Forrest decide to run for a quite long time？

Why does Forrest decide to run for a quite long time？
A.Because he wants to find Jenny.
B.Because it’s a promise to his mother.
C.Because he loves running.
D.Because he feels lonely and aimless after Jenny’s leaving and his mother’s death.
正确答案：Because he feels lonely and aimless after Jenny’s leaving and his mother’s death.