The correct answer is A. Cold, dense ocean water sinking and warmer water replacing it.
Thermohaline circulation is a global ocean circulation that is driven by differences in temperature and salinity. The main driving force of thermohaline circulation is the sinking of cold, dense water in the North Atlantic Ocean. This sinking water is replaced by warmer, less dense water from the tropics. The thermohaline circulation is important because it helps to distribute heat and nutrients around the globe.
Option B is incorrect because winds do not cause the sinking of cold, dense water. Option C is incorrect because warmer, less dense water does not sink in the ocean. Option D is incorrect because warm water is not added to the ocean due to industrial waste.