Questions: Both involve the kidneys. Both are carried out by the urinary system. Both eliminate waste from the body. Both are carried out by the digestive system. Both involve the colon.

The answer is the third one: Both eliminate waste from the body.

Explanation for each option:

1. Both involve the kidneys: Incorrect. Excretion involves the kidneys, but defecation does not. Excretion is the process of removing waste products from the blood, primarily through the kidneys, which produce urine.

2. Both are carried out by the urinary system: Incorrect. Excretion is carried out by the urinary system, but defecation is not. Defecation is part of the digestive system, where solid waste is expelled from the body.

3. Both eliminate waste from the body: Correct. Both excretion and defecation are processes that eliminate waste from the body. Excretion removes liquid waste through urine, while defecation removes solid waste through feces.

4. Both are carried out by the digestive system: Incorrect. Only defecation is carried out by the digestive system. Excretion is primarily a function of the urinary system.

5. Both involve the colon: Incorrect. Only defecation involves the colon, as it is part of the digestive system where feces are formed and expelled.

In summary, both excretion and defecation are processes that eliminate waste from the body, but they involve different systems and types of waste.