What is Pangaea?
 A. 
 A single, large landmass in which all of Earth's continents were once joined.
 B. 
 A mid-ocean ridge than runs from north to south along the Atlantic Ocean's floor.
 C. 
 A species whose fossilized remains in Africa led to the hypothesis of continental drift.
 D. 
 A complex theory that explains the motions of continents and many of Earth's features.