Which Best Describes the El Niño-Southern Oscillation

Which best describes the El Niño-Southern Oscillation?

A) It occurs every year around Christmas time in the southern Pacific Ocean.
B) It is a periodic shift of high and low pressure zones over the western and eastern Pacific,respectively,usually occurring every 2 to 12 years.
C) It is a pattern of sea surface,air pressure,and wind shifts between the northern and tropical western Pacific,usually occurring once every 20 years.
D) It is a north-south fluctuation of high and low pressure zones in the North Atlantic Ocean.