Excretion is the process of removal of nitrogenous waste like urea,uric acid,ammonia and metabolic waste.
But removal of faeces from the body is known as egestion.
So in the given options egestion is not the removal of metabolic waste.

Introduction:
Excretion is the process of removing waste products or harmful substances from the body. It involves the elimination of metabolic waste products that are produced during various physiological processes. While the removal of faeces or undigested food from the body may seem like a form of excretion, it is not considered an example of excretion because of the following reasons.

Explanation:

a) Faeces is given out of the alimentary canal:
- The faeces, which consist of undigested food, fiber, bacteria, and other waste materials, are formed in the large intestine.
- They are then eliminated from the body through the rectum and anus.
- This process is not related to the excretory system, but rather the digestive system, as it involves the elimination of waste materials that have not been absorbed or digested by the body.

b) It has not been digested by the body:
- Faeces consist of undigested food that has passed through the digestive system without being broken down or absorbed.
- Digestion is a process that occurs in the digestive system, where food is broken down into smaller molecules that can be absorbed by the body.
- Since undigested food has not been processed or metabolized by the body, it cannot be considered a product of metabolism, which is a key characteristic of excretory waste.

c) Undigested food is not a product of metabolism:
- Excretion primarily involves the removal of waste products that are produced as a result of metabolic processes in the body.
- Metabolism refers to the chemical reactions that occur within cells to convert nutrients into energy and other necessary molecules.
- The waste products of metabolism include substances like carbon dioxide, urea, and excess salts, which are filtered out by the excretory organs, such as the kidneys.
- Undigested food, on the other hand, is not a product of metabolism but rather a result of incomplete digestion or inadequate absorption in the digestive system.

d) If it remains in the body, it produces foul gases:
- While the presence of undigested food in the body may lead to discomfort or gas production, this is not a defining characteristic of excretion.
- Foul gases, such as methane and hydrogen sulfide, are produced by the action of bacteria on undigested food in the large intestine.
- The elimination of these gases is primarily a result of the digestive process rather than the excretory process.

Conclusion:
In conclusion, the removal of faeces or undigested food from the body is not considered an example of excretion because it does not involve the elimination of metabolic waste products. Excretion primarily involves the removal of waste materials that are byproducts of metabolic processes in the body, while the elimination of undigested food is a function of the digestive system.