Which of the following is not a waste that is removed from the body through excretion?

a. blood

c. carbon dioxide

b. salt

d. urea

The correct answer is a - blood.

Blood is a tissue. It is kind of connective tissue composed of an aqueous fluid called plasma in which are suspended three components namely red blood cells, white blood cells, and platelets.

Two main functions of blood is transport of substances to and from each cell in the body, and to provide immunity and protection against invading pathogens.

It is therefore not a waste product but it carries waste products such as carbon dioxide to the lungs to be expelled.