Upon arriving home I was surprised to find the paper I had had was missing.A. to be prep

问题补充：

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

答案：

A. to be prepared

B. to prepare

C. preparing

(答案→)D. prepared

解析：考查have sth done“请人做，使…被做”词组，分析句子the paper后面是定语从句，两个had，一个是助动词，一个是使役动词，在定语从句中从当宾语的关系代词被省略，prepare和the paper是被动关系，选D，意为：一到家，我很惊讶的发现我准备好的文件不见了。