I don't really agree with the whole idea of global warming, but the only question that makes the most sense (besides increase in salinity) is A. melting of glaciers and ice caps. Reason being: precipitation generally originates from oceans, and the ocean can't rise from raining with it's own water, increase in water density is (as far as I know) impossible, and expansion of water volume is, basically, just re-wording the phrase "sea level rising" (volume means taking up more space).
