Mountains that are formed between two large faults are known as
a. seamounts.
b. fault-block mountains.
c. uplifted mountains.
d. plateaus.

The correct answer is B.

Fault block mountains form when faults or cracks  in the earth's crust  force materials or blocks of rocks downward and others upwards.

This happens when instead of the earth folding over, the earth's crust  pulls apart breaking up into chunks or blocks . These blocks get stacked on each other with some projecting up above the  surface of the crust forming a mountain. Such mountains usually have a steep front side and a sloping back side.