Which letter indicates the most gradual change in temperature?

Explanation:

The climate of the United States varies due to changes in latitude see in the regions of united states. There is also range of geographic features, including the mountains , biodiversity and deserts. Seen on the mainland, the climate of the U.S. becomes warmer the further when traveled towards west till the coast is reached. The alteration in latitude makes the land dryer as its moved.

answer; /// i believe the correct answer is general act charters;