Mountains that form when large areas of earth gradually move skyward as a unit are called mountains.
a. low-lying
b. impoverished
c. uplifted
d. improvisation

Mountains that form when large areas of Earth gradually move skyward as a unit are called "uplift mountains" or specifically "tectonic uplift mountains", since the tectonic plates beneath are colliding. 

Mountains that form when large areas of Earth gradually move skyward as a unit are called C.Uplifted Mountains.