英语中的主被动情况?Micheal put up a picture of Yao Ming beside the be

英语中的主被动情况?
Micheal put up a picture of Yao Ming beside the bed to keep himself ( ) of his own dreams.
A.reminding B.to remind C.reminded D.remind
正确答案是C,理由是himself与remind之间是被动关系.但是我觉得Micheal为了激励自己去记住自己的梦想应该是“主动去记住”啊?怎么是被动?
话说一直对外语里的主被动方式不大分得清.比如worker与buildings之间如果是从worker出发就是“工人主动盖楼房”,但是如果从buildings出发就是“楼房被工人盖”,那么在句子中到底怎么认定主被动方式呢?