Circulatory system transports these throughout the body

(a)

Oxygen

(b)

Nutrient

(c)

Hormones

(d)

All of these

Main organ of respiration in human body is

(a)

Stomach

(b)

Spleen

(c)

Heart

(d)

Lungs

Breakdown of food into smaller molecules in our body is known as

(a)

Muscle contraction

(b)

Respiration

(c)

Digestion

(d)

Excretion