Here's a problem to solve: Why do areas in the middle of a large continent generally have more extreme differences in temperature than areas near the coastline?

Among the 4 following options, which is the correct answer?

- A: There are generally more clouds near the oceans.
 
- B: Landlocked areas are usually at a lower altitude than coastline areas.
 
- C: Coastlines are usually surrounded by mountains that block air masses.
 
- D: Oceans change temperature slowly and regulate the temperature of nearby land.
 