Sentence Correction

Hey Guys,

I don't need much help for RC or CR but for SC I've always had very ordinary scores. I've watched a few online videos and read The Manhattan GMAT Sentence Corection, 12th Ed. Its helped but not enough. So firstly feel free to recommend a better source of information. Secondly I've found long passages a little overwhelming and confusing. As in, Im not sure what to "match" (parallel, modifiers, subject-verb agree, etc) what to look for as errors and so on. Its all the commas and it becomes a little confusing. For example the question below what should I look for to easily resolve the question?
All the commas confuse me as to what should match what, so how can I simply it to answer it easily? Thanks guys

Dressed as a man and using the name Robert Shurtleff, Deborah Sampson, the first woman to draw a soldier´s pension, joined the Continental Army in 1782 at the age of 22, was injured three times, and was discharged in 1783 because she had become too ill to serve.

A. 22, was injured three times, and was discharged in 1783 because she had become
B. 22, was injured three times, while being discharged in 1783 because she had become
C. 22, and was injured three times, and discharged in 1783, being
D. 22, injured three times, and was discharged in 1783 because she was
E. 22, having been injured three times and discharged in 1783, being