Which of the following is a possible reason for sleep?

a) growth

b) digestive

c) speed

d) intelligence

Answer: a). growth

Sleep is a necessary biological activity shown by most of the living creatures. It is the primary activity of the brain. During sleep the blood supply to the muscles increases, the energy of the body gets restored, repair and tissue and growth takes place. Important hormones are released for the process of growth and development.

Therefore, sleep is necessary for growth is a correct option.