While Visiting the South Island of New Zealand, You Notice

While visiting the South Island of New Zealand, you notice that conditions vary sharply across the island.The West Coast is very wet and receives between 600 and 1600 mm of rainfall per year, while the East Coast only receives about 640 mm of rain per year and is very dry.What best explains this regional difference in precipitation?

A) Proximity to Antarctica.
B) The absence of inland lakes.
C) The presence of a large river along the West Coast.
D) The presence of mountains along the West Coast.