In a plan to stop the erosion of East Coast beaches, the Army Corps of Engineers proposed building parallel to shore a breakwater of rocks that would rise six feet above the waterline and act as a buffer, so that it absorbs the energy of crashing waves and protecting the beaches.
(A) act as a buffer, so that it absorbs
(B) act like a buffer so as to absorb
(C) act as a buffer, absorbing
(D) acting as a buffer, absorbing
(E) acting like a buffer, absorb
Parallelism--that would rise and act
So that leaves us with A,B,C. act like vs. act as. Act like means act similar to. Act as means function as. Here Act as is correct use meaning wise. So between A and C, we have so that it absorbs vs. absorbing.
There is one more parallelism here. absorbing anf protecting. So D is correct.
Hope this post helps!
Your kudos will let me know.