Answer:
A: Applied force
Step-by-step explanation:
The rest of them are non-contact forces.
A contact force is any kind of force that requires contact to occur.
So:
Applied force is a contact force because they occur ONLY during contact with each other.
Gravitational force is not a contact force because they occur even when they're not in contact with each other.
Electrical force is not a contact force because they also occur even when they aren't in contact with each other.
Magnetic force is not a contact force because they pull/push on objects without touching them.