It is easier to pull a lawn roller than to push it because pulling:
(A) Involves sliding friction
(B) Involves rolling friction
(C) Increases the effective weight
(D) Decreases normal reaction

Hint: When a body moves on a plane it will come to rest after some time. This is due to an opposing force acting at the surface of contact. This opposing force is called the frictional force or friction. The frictional force acts tangential to the surface of contact.

Complete answer:
We can resolve the force acting on the lawn roller into two components. The sine component of the force is parallel to the surface on which the roller moves. The other component is the cosine component which is perpendicular to the surface.
When the lawn roller is pulled, the normal component decreases that means the cosine component of force decreases. Therefore the frictional force also decreases. But if we push the lawn roller the normal force increases that means the cosine component of force increases. This will increase the frictional force. Therefore we can say that it is easier to pull the lawn roller than to push it because the normal component of force decreases when the lawn roller is pulled.

Therefore, It is easier to pull a lawn roller than to push it because pulling Decreases normal reaction. So, option (D) is correct.

Additional information:
Friction has many advantages as well as disadvantages. The reason why we are able to walk on the ground, we can hold objects in our hands, etc. is friction. But the disadvantages of friction are that the fuel consumption of vehicles increases due to friction. The wear and tear of machine parts is also a disadvantage of friction.

Note: The frictional force is of two types that are the static friction and kinetic friction. The frictional force between the surfaces of two bodies that are in contact, when the bodies are at rest is called static friction. Kinetic friction is experienced by the surfaces of bodies that have contact and are moving.