问一个英语单选题---Have you checked all the relief ------- to the pe

问一个英语单选题
---Have you checked all the relief _______ to the people in the drought-hit areas?
---Yes,several times.But I'll check it once more
A.sent B.sending C.to send D.to be sent
这道题选D,为什么不能选A呢,不是用过去分词直接表示被动吗?