The correct answer is B. Kidneys.
The kidneys are the primary organs of excretion in mammals. They filter the blood and remove waste products, such as urea, creatinine, and uric acid. The kidneys also regulate blood pressure and produce hormones that help to control red blood cell production and bone metabolism.
The large intestine is responsible for absorbing water and electrolytes from the digestive tract. It also stores feces until they are eliminated from the body.
The lungs are responsible for gas exchange. They take in oxygen from the air and deliver it to the blood, and they remove carbon dioxide from the blood and release it into the air.
The liver is a vital organ that performs many important functions, including detoxification, metabolism, and bile production. However, it does not play a major role in excretion.
In conclusion, the kidneys are the primary organs of excretion in mammals. They filter the blood and remove waste products, such as urea, creatinine, and uric acid. The kidneys also regulate blood pressure and produce hormones that help to control red blood cell production and bone metabolism.