HELP!大全524

1.        Ms. Wright tries to get inside Iran to understand how it works, the role it has played in the Middle East and its intricate relationship with the United States, which is complex and depends heavily on understanding of the Farsi language.

(A) which is complex and depends

(B) because it is complex and depends

(C) but they are complex and depend

(D) which are complex and depend（E）

(E) a task that is complex and depends

答案是E

句子的结构是什么？

the role 和a task并列作前面句子的同位语吗？没有and连接，空空两个名词放在一起？