Which of the following best explains why the older fold mountains are much lower and less rugged than the newer ones?

A.

The newer fold mountains are situated in areas of active earth movements

B.

The effects of earth movements resulting in mountain building are much greater nowadays than they were during the period of folding

C.

The newer fold mountains, in contrast to the older ones, are made up of more resistance rocks

D.

The older fold mountains have been subjectd to the forces of denudation for longer, geological periods

E.

Most of the newer fold mountains are situated in the interior parts of continents where they are free from constant sea erosion

Correct answer is D

No explanation has been provided for this answer.