mid-ocean ridges desert sand dunes U-shaped valleys continental shelves
I gave my students this multiple choice question: Which of these features of Earth's crust are caused by the shifting of tectonic plates?

Only one answer is correct among these 4 choices:
- mid-ocean ridges
- desert sand dunes
- U-shaped valleys
- continental shelves

Could you tell me which one is correct?

mid-ocean ridges