Final answer:
El Niño is characterized by warmer-than-average sea surface temperatures in the Pacific Ocean, while La Niña features cooler temperatures. La Niña is not associated with weakened trade winds; rather, it reinforces them, possibly increasing rainfall in certain areas unlike a decrease suggested in the statement.
Step-by-step explanation:
If we consider El Niño and La Niña relative to normal atmospheric/oceanic conditions, the correct statement is: a) El Niño is characterized by warmer-than-average sea surface temperatures in the Pacific. El Niño refers to the phase of the El Niño Southern Oscillation (ENSO) where there is a band of warm ocean water that develops in the central and east-central equatorial Pacific, resulting in higher air pressure in the western Pacific and lower air pressure in the eastern Pacific.
In contrast, La Niña represents the cool phase of ENSO and is marked by below-average sea surface temperatures in the eastern Pacific, coupled with high air pressure in the eastern Pacific and low in the western Pacific. It is not associated with weakened trade winds, that is a characteristic of El Niño. La Niña typically results in more intense trade winds, and while it could lead to decreased rainfall in regions such as the southwestern United States, it tends to increase precipitation in the western Pacific.