Final answer:
A a. normal fault is under tension, as tensional forces cause the hanging wall to move down relative to the footwall.In a normal fault, tensional forces cause the hanging wall to move down relative to the footwall.
Step-by-step explanation:
Types of Faults
There are three main types of faults: normal faults, reverse faults, and strike-slip faults. Normal faults occur when the hanging wall moves down relative to the footwall, and they are formed during extension. Reverse faults, on the other hand, occur when the hanging wall moves upwards relative to the footwall, and they are formed during compression. Lastly, strike-slip faults occur when there is horizontal displacement along the fault plane.
Fault under Tension
In the context of the question, the type of fault that is under tension is a normal fault. In a normal fault, tensional forces cause the hanging wall to move down relative to the footwall. This type of fault is commonly associated with areas of crustal extension, such as divergent plate boundaries.