Why does your body get more rest when you're lying down than it does when you're sitting?
A. Body exerts less pressure while lying down
B. Body exerts more pressure while lying down
C. Body exerts zero pressure while lying down
D. None of these

Hint: With the increase in weight or decrease in surface area of an object the pressure exerting on the surface decreases or we can say that pressure exerting on the object is inversely proportional to the surface area of the object.

Complete step by step answer:
Pressure is defined as force per unit area.
$\text{Pressure} = \dfrac{\text{force}}{\text{area}}$
This gives the relationship between pressure and surface area.
$\text{Pressure} \propto \dfrac{1}{\text{area}}$
Hence we can conclude that with the increase in surface area of a body the pressure exerted by that body decreases and vice versa.So, when we are lying down the area of contact of our body with the ground is more, therefore, the surface area is more hence the body exerts less pressure while lying down and our body gets more rest.

When we are sitting the area of contact of our body with the ground is less so the surface area of the body touching the ground decreases hence the body feels more pressure. Also while sitting there is a strain in our body so that our upper body stays straight, hence the body does not get more rest.

Therefore option A is the correct answer.

Note: When we are sitting on a chair there are two types of forces acting on the body: Gravitational force acting downwards and an upward push by the chair in the upward direction. Both these forces are equal to each other hence we can say net force on the body is equal to zero. When the net force is zero the motion of an object does not change.