As you descend through the water column,
a.
temperature decreases.
b.
pressure decreases.
c.
light increases.
d.
density decreases.

A because its gets too cold because the light does not enter, It cannot be Because if the pressure decreses then the water has to have not mass pushing down and weightless, It cannot be C neither because light cannot travel far through water, And at last D the density covers anything of its mass weight . 

Due to the amount of pressure