谁能帮分析一下这是啥从句.

题目

谁能帮分析一下这是啥从句.
Attached is one of the characters based upon which the flash game for iphone, ipad and computer is to be developed.
我个人觉得这是定语从句：based upon 前省略了（Which is）此定语从句用来修饰 one of the characters。
而based upon 后面的 Which是作为定语从句中嵌套的宾语从句，作为based upon的宾语。
有高人么，给说说~

答案

Attached is one of the characters based upon which the flash game for iphone,ipad and computer is to be developed.
which the flash game for iphone,ipad and computer is to be developed.宾语从句