Question

Excretion is the removal of-
(a)Carbon dioxide
(b)Harmful and useless ingredients
(c)Extra water
(d)Metabolic waste

Answer 1

Hint: Excretion is a mechanism by which an organism removes waste. This is mainly carried out by the lungs, kidneys, and skin in vertebrates. This is in contrast with secretion, where after leaving the cell, the material can have unique tasks.

Complete answer:
Excretion is the elimination from the body of metabolic waste products. Carbon dioxide, urea, ammonia, uric acid, guanine, etc. are the main excretory products. The accumulation in the body of excretory materials serves as a toxic agent for the cell and impedes metabolic activity. In humans, the main excretory organ is the kidney. The lungs, skin, etc. are other organs of excretion.

Additional Information: Humans have two forms of waste to get rid of. Digestive system waste (feces) and metabolic activity waste (sweat & urine). Egestion is known as the elimination of intestinal waste (pooping). Metabolic waste reduction is called excretion.
 The flow of the breath out of an organism is exhalation (or expiration). ... Exhaled air, which is processed as ATP, is rich in carbon dioxide, a waste product of cellular respiration during energy production.
Urination is the transfer of urine through the urethra to the outside of the body from the urinary bladder. It is a type of excretion in the urinary system.
So, the correct answer is ‘metabolic waste’.

Note: All the metabolic waste is excreted into the excretory organs in the form of water solutes (nephridia, malpighian tubules, kidneys), with the exception of CO2, which is excreted in the lungs along with water vapor. The removal of these substances allows for the organism's chemical homeostasis.