The Himalayan Mountains Are Rugged, Jagged Peaks and the Appalachians

Multiple Choice

The Himalayan Mountains are rugged, jagged peaks and the Appalachians are smooth and rolling. Why is there a difference

A) The Himalayas are much older and the rocks have begun breaking off.
B) The Himalayas are volcanic mountains and the Appalachians are not.
C) The Appalachians are much older and have been smoothed by erosion.
D) The Appalachians are younger and just started to be thrust upward by plate tectonics.
E) a and d