[单项选择]

El Nino is the term used for the period when sea surface temperatures are above normal off the South American coast along the equatorial Pacific, sometimes called the Earth’s heartbeat, and is a dramatic but mysterious climate system that periodically rages across the Pacific.
El Nino means "the little boy" or "the Christ child" in Spanish, and is so called because its warm current is felt along coastal Peru and Ecuador around Christmas. But the local warming is just part of an intricate set of changes in the ocean and atmosphere across the tropical Pacific, which covers a third of the Earth’s circumference. Its intensity is such that it affects temperatures, storm tracks and rainfall around the world.
Droughts in Africa and Australia, tropical storms in the Pacific, torrential rains along the Californian coast and lush greening of Peruvian deserts have all been ascribed to the whim of EI Nino. Until recently it has been returning a
A. a description of a scene
B. a root cause of EI Nino
C. a narrative of an event
D. a definition of EI Nino

El Nino is the term used for the period when sea surface temperatures are above normal off the South American coast along the equatorial Pacific, sometimes called the Earth’s heartbeat, and is a dramatic but mysterious climate system that periodically rages across the Pacific.
El Nino means "the little boy" or "the Christ child" in Spanish, and is so called because its warm current is felt along coastal Peru and Ecuador around Christmas. But the local warming is just part of an intricate set of changes in the ocean and atmosphere across the tropical Pacific, which covers a third of the Earth’s circumference. Its intensity is such that it affects temperatures, storm tracks and rainfall around the world.
Droughts in Africa and Australia tropical storms in the Pacific, torrential rains along the Californian coast and the Peruvian deserts have all been ascribed to the whim of El Nino.
This at least is the theory, and it has work
A. The water temperature is above normal.
B. Sea surface temperatures are higher than usual.
C. The water temperature is below normal.
D. Sea surface temperatures are lower than normal.