Question

which of these is associated with el niño?
a. below - average sea levels
b. below - average sea surface temperatures
c. a periodic warming of sea surface temperatures
d. periodic rises in carbon dioxide levels

Explanation:

El Niño is characterized by a periodic warming of sea surface temperatures in the central and eastern tropical Pacific Ocean. Below - average sea levels are not a main feature of El Niño. Below - average sea surface temperatures are more related to La Niña. Periodic rises in carbon dioxide levels are mainly due to human activities (like burning fossil fuels) and not a direct characteristic of El Niño.

Answer:

C. A periodic warming of sea surface temperatures