Which is a simple sentence?

 - If we hike Bright Angel Trail in the Grand Canyon, we won't see Mooney Falls.
 - Madison Chock and Gracie Gold were two American figure skaters in the Sochi 2014 Olympics.
The first sentence is the simple sentence. It is a single independent clause.
Madison Chock and Gracie Gold were two American figure skaters in the Sochi 2014 Olympics.