Identify the true statement.
choose one:
a. water from rivers or rain tends to stay in a layer above saltier water for quite a while before it mixes.
b. saltier water generally floats above fresher water.
c. the boundary between surface-water salinities and deep-water salinities is called the thermocline.
d. when seawater evaporates, salt is removed in the vapor, leaving behind fresher water.