The correct answer is B. When surface waters in the eastern Pacific are colder than normal
Step-by-step explanation:
La Niña is a weather phenomenon that occurs as ocean water and more especially surface water temperature decreases or is colder than normal. This the opposite of El Niño that makes surface water to be warmer. Besides this, due to the changes in ocean temperature, this phenomenon has effects on weather such as more rainfall in multiple areas including parts of Asia, South America, and southern Africa while in others areas such as the U.S. it causes drier weather conditions. This phenomena only occurs in the surface water and usually near the equator zone in the eastern Pacific. Accoridng to this, La Niña occur "when surface waters in the eastern Pacific are colder than normal".