Coastal communities often experience milder winters and cooler summers than further inland because of which of these factors?

This is due to the presence of the sea and the accompanying winds. Both of      these factors help coastal communities retain more heat during the winters and are also able to cool off easier in the summers, thus having cooler summers and milder winters.  

The coastal communities experience milder winters and cooler summers than the people residing further inland because the coasts are governed by the presence of humidity in the local weather.

Explanation:

Coastal areas tend to have moderate temperatures both in the winters and the summers due to the influence of humidity in the local coastal atmosphere. The wind blowing over the coast carry moisture making the summers seem cooler, whereas, the same moisture that is due to the warms ocean water makes the winters seem milder.

The correct answer is a)  a resource with a limited supply; it will run out.