Most people in southern North America live in which climate zone?

Temprate zone.

Explanation:

Typically,  temperate zone has warm summers with decently high humidity. The winters also considered to be mild  with an average of 36°F - 55°F.  It is very common for this region to encounter thunderstorms and hurricanes.

Beside the winter period, the climate in southern part of North America generally really suitable for farming. Which is probably the reason agriculture is considered one of the largest contributor in southern states' economy.

c. reserves power to the states and people