Rocks and sand on beaches become rounded rapidly because ________.

A) the swash action of waves rolls loose material up and down the beach, where it is abraded rapidly to produce rounded grains
B) rip currents move the sand offshore rapidly, abrading the fragments
C) Beach sand is mostly calcium carbonate from reefs and so gets rounded easily
D) There is nothing particularly prominent in beaches that produces more rounding than other sedimentary processes.