keep是系动词，为什么不用主动表被动？

.-Your job---- open for your return
-Thanks
A will be kept B will keep C had kept D had been kept 答案是A，为什么呢？不是系动词用主动表被动吗？keep是系动词呀

KEEP是情态动词吗 keep awake 为什么不能是keep waking 为什么有的动词后的词要加-ing？如keep doing? stay ,remain , keep 做系动词 ”保持”的区别 worry是一个动词，但为什么常用be worried about而不用worry about warm 是形容词，为什么可以是keep warm ,而不是keep warmly？谢谢解答． He feels differently 中为什么用differently 而不用different。feel不是系动词吗？ Pecking apples is interesting.中的系动词be 为什么用is而不用are呢？ You stupid creature!stupid是形容词啊``前面不用加系动词吗? i feel hurt.这里feel已经是系动词,为什么还用动词hurt