If old mountains wear down over the course of millions of years, what is one of the primary reasons that mountains still exist? a. new mountains are created from decomposition of trees. b. new mountains are created from leaf litter. c. new mountains are created through tectonic and volcanic activity. d. new mountains are created through city development.

The correct answer is: C) New mountains are created through tectonic and volcanic activity.

There are three ways in which mountains are formed, therefore there are three different types of mountains: volcanic, fold and block mountains.

It is important to say that these always involve plate tectonics, were huge "compressional forces, isostatic uplift and igneous (magma) matter, forces surface rock upward". In this way a landform higer than the surroundings is created, that is to say: a mountain.

There is no way a mountain is created by one of the other options given.