Gravitational force is a conservative force, but frictional force is non-conservative Why ?

Explanation

A conservative force is one for which the work done can be restored. To lift a body work has to be done against gravity. This work gets stored in the body as its potential energy. The body, while returning to its initial state, does the same amount of work using that stored potential energy. hence , gravitational force is a conservative force.
If the work done against a force cannot be restored , the force is called non-conservative. To pull a body over a rough surface, work has to be done against frication. This work done can never be recovered. To return the body to its initial state, again work has to be done against friction. so, friction is a non- conservative force.