The correct answer is - D. Pacific.
The El Nino climate pattern is still confusing for the scientists as they still can not figure it out why is it happening. It occurs on every four years, in the eastern part of the Pacific Ocean. It warms up the eastern part of the Pacific, while cooling off the western part of it in meantime. El Nino manages to have global impact on the climate, and in some places that means lots of precipitation and colder weather conditions, while in others prolonged droughts and warmer weather conditions.
The most affected region in the world by El Nino is the western part of thew South American continent.