Hello Everyone!
It looks like we’re dealing with a list here, and we know that means one thing: parallelism! Any time you see a list on the GMAT, the first thing you should always do is make sure each item is written using parallel structure!
Let’s see how each answer holds up:
(A) which permeates the bone, washes away its organic components, and replaces them --> CORRECT
(B) which permeates the bone, washes away its organic components, and those are replaced --> INCORRECT
(C) which permeates the bone, washing away its organic components, to be replaced --> INCORRECT
(D) permeating the bone, washing away its organic components, to be replaced --> INCORRECT
(E) permeating the bone, washing away its organic components and replacing them --> INCORRECT
So why is E incorrect, even though it uses parallel structure? The GMAT requires the use of the serial comma (aka the Oxford comma) for the last item in a list of 3+ items. Answer E doesn’t use a serial comma, so it’s wrong.
Don’t study for the GMAT. Train for it.