Answer: Option (a) is the correct answer.
Step-by-step explanation:
The measure of amount of salt dissolved in ocean is known as ocean’s salinity.
Therefore, when salinity increases then mass of salt in the ocean increases as a result the density will increase.
As density is the mass per unit volume of a substance. Mathematically, it is as follows.

Therefore, when mass increases then density will increase as there is no change in volume.
Whereas salinity increases when there is an increase in temperature as more salt will dissolve then in the ocean but due to increase in salinity there will be no effect on temperature. Hence, temperature will neither increase or decrease due to the increase or decrease in salinity of ocean.
Thus, we can conclude that when the ocean’s salinity increases then the density increases.