turn to sth as ..vs turn to sth for

by **tankobe** Mon Jan 25, 2010 11:50 pm

Once again O'Dell turns to the Native American for his subject, and in this novel he brings to life the mysterious Shoshone girl Sacagawea, interpreter and guide for Lewis and Clark.
(A) for his suject
(B) his subject
(C) as his subject
(D) to use as his subject
(E) to use as subject
source--from a book review:http://www.amazon.com/Streams-River-Sea-Novel-Sacagawea/dp/product-description/0395404304

this is not a real GMAT question, but it is a similar one. could anyone explain the advantage or disadvantage of each option?