Final answer:
The statement is not completely correct; the Himalayas and the Ural Mountains were formed by continental collisions, but the Appalachian Mountains' formation involved a series of complex events, including collisions with island chains and Gondwana.
Step-by-step explanation:
The statement that the Himalayan, Ural, and Appalachian mountain systems were all formed as a result of a continental crust collision is partially true and partially false. The Himalayas and the Ural Mountains were indeed formed by the collision of continental plates. Specifically, the Himalayas formed at a continent-continent convergent boundary between the Indian and the Eurasian plates, while the Ural Mountains were created during an orogeny that occurred when the continental landmasses of Kazakhstania and Baltica collided.
However, the formation of the Appalachian Mountains differs slightly; they are the product of multiple collisions, primarily small island chains and culminating with a collision with the supercontinent of Gondwana during the formation of Pangaea. The Appalachians have been significantly eroded over time. The Appalachians, especially, indicative of a complex tectonic history that involved more than just a simple continental collision.
Thus, while mountain building often involves collisions between continents, the processes can vary, including additional events such as subduction and volcanic activity.