问题详情：
Upon arriving home，I was surprised to find the paper I had had ________ was missing.
A．to be prepared B．to prepare
C．preparing D．prepared
【回答】
D [考查非谓语动词。句意：我一到家就惊奇地发现我事先让人准备的文件不见了。(that/which)I had had prepared是定语从句，修饰先行词the paper，从句中含有一个have sth done 结构，表示“让别人做某事”。]
知识点：非谓语动词
题型：选择题
