The correct answer is - convergent plate boundary.
The folded mountains of Pennsylvania, part of the Appalachian Mountain Range, are mountains that have been formed by plate collision. This has occurred in the Ordovician period, when the continents were merging and were establishing the super-continent Pangaea.
The Himalayas are a much more recent formation, bu the process had been the same. The Indian plate had been moving towards the Eurasian plate, and eventually collided with it. Because of the enormous pressure, the land started to lift up, and eventually created the highest mountain range in the world.