the watch was very good,and he ------- 20 percent down for i

the watch was very good,and he _______ 20 percent down for it. a.paid b.cost c.bought d.spent
这是广东省的一道高考题,为什么是选A?（我们老师讲的,我去网上查了也是选A）
但是bring down不是有压价的意思吗?不是应该选C吗?
请详细解答,谢谢~~