What kind of stress form fault-block mountains

Fault-block mountains are formed by extensional stresses.

Explanation:

Fault-block mountains are formed because of extensional stresses. They are also called tension stresses. These stresses pulls and stretches rocks apart which causes normal faults to form. The normal fault cuts through rocks, causing one to slip downward and one to move upward. Thus, fault-block mountains are formed. Sierra Nevada in California and Nevada is an example of a fault-block mountain.