885section 14 -No. 4,A为什么不对?so that 不是不能随意添加或丢失吗?

885section 14 -No. 4

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（C）

(E) acting like a buffer, absorb

A为什么不对?so that 不是不能随意添加或丢失吗?