Answer:
The correct answer is option b, that is, the calming down of trade winds in the Pacific, which leads to the buildup of warm water.
Explanation:
A natural phenomenon, which is observed in the southwestern part of the Pacific known as El Nino is signified by the calming down of the trade winds in the mentioned part of the Pacific Ocean. With the calming of the trade winds, the water begins to warm up, while at the same time, the water gets cooled down on the contrary section of the Pacific Ocean.