NOTES : Infinitives as second verb.

The GMAT fanatically prefers the second verb in a set to be in infinitive form. 

Before the Civil War, Harriet Tubman, herself an escaped slave, returned again and again to Maryland to guide other slaves along the Underground Railroad to freedom. 

(A) herself an escaped slave, returned again and again to Maryland to guide 

(C) an escaped slave herself, returned again and again to Maryland for guiding 

So, on the GMAT, you should always pick "returned to guide" over "returned for guiding".