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

(E) acting like a buffer, absorb

答案如何是C呢？as 应该接句子阿，怎么能接一个词组呢?

Analyze the following sample sentence:

John served as an engineer, but he always acted like a general manager.