Respuesta :
We have that cold water in general is more dense than hot water (except when around the freezing point of water, which is not the case in vents) because hot water expands. Also, salt is more dense than water and thus mixing salt with water makes the resulting water more dense. The more salt you add, the denser the product. Hence, we get that the water get denser with lower temperatures and higher salinities. Thus, a is correct.