Complete the following sentence: As the data moves down through the layers of the OSI reference model, before passing it down to a lower layer, each OSI layer _____________________.

Complete the following sentence: As the data moves down through the layers of the OSI reference model, before passing it down to a lower layer, each OSI layer _____________________.
A. adds a header and (if applicable) a trailer
B. adds a header after stripping the header added by the previous layer
C. adds both a header and a trailer
D. adds only a header