The value of sliding friction for an object can be determined by the force required to move the object from rest. In this case, it is given that the object requires 7 N of force to move it from rest.

The force required to overcome sliding friction can be calculated using the equation:

Force of sliding friction = coefficient of sliding friction * normal force

The coefficient of sliding friction is a dimensionless constant that depends on the nature of the surfaces in contact. The normal force is the force exerted by the surface on the object perpendicular to the surface.

In this case, since we are only given the force required to move the object and not the coefficient of sliding friction or the normal force, we cannot directly calculate the value of sliding friction. However, we can make an inference based on the given information.

To move the object from rest, a force of 7 N is required. This force must be greater than or equal to the force of sliding friction. If the force of sliding friction were equal to 7 N or greater, the object would not move as it would be balanced by the frictional force. Therefore, option 'b' (Greater than 7 N) can be eliminated.

If the force of sliding friction were equal to 7 N, the object would just barely move, but it would not accelerate. However, since the object is said to require 7 N of force to move it from rest, this implies that there is an additional force acting on the object, such as an applied force or an external force, to overcome the sliding friction and allow the object to accelerate. Therefore, option 'a' (7 N) can also be eliminated.

Considering the above analysis, the only remaining option is option 'c' (Less than 7 N). This means that the force of sliding friction is less than 7 N, and there must be an additional force to overcome the sliding friction and move the object from rest.