The diagram above illustrates that two types of currents are found in ocean waters. Which is the BEST explanation for why oceans have two different types of currents?
A:Surface currents are caused by wind whereas deep currents are caused by differences in density.
B:Surface currents are caused by differences in density whereas deep currents are caused by wind.
C:Surface currents are caused by changes in salinity whereas deep currents are caused by changes in temperature.
D:Surface currents are caused by temperature differences whereas deep currents are caused by changes in salinity.