The Köppen classification system is used as a classification system for

A. low-pressure systems.

B. high-pressure systems.

C. weather systems.

D. climates

This is a classification system for climates: the correct answer is D.

The major classification is into tropical, dry, temperate, continental and polar climates.

For example, the continental climates have an average temperature around 10 Degrees Celcius in the summer and - 3 Degrees in the winter.

All those types have further sub-divisions.