The correct options are
B If prevailing winds are onshore, they lead to increase in the temperature of ocean water.
C Offshore prevailing winds decrease the temperature of ocean water.
D Offshore winds lead to a displacement of coastal water by colder deep sea water.
Prevailing winds are those surface winds that blow consistently over a particular region on the Earth. If these winds are onshore, they will push the ocean's surface water towards the coast which raises the ocean temperature. On the other hand, offshore winds will drive the water away from the coast. This displaced water gets replaced by the water from the bottom of the ocean. The water from the bottom of the ocean tends to be very cold as the penetration of sun's rays decreases with increasing depth. Hence, offshore winds decrease ocean temperature.