Which of the following is the longest part of the alimentary canal ?

Small intestine 

The correct answer is Option (3) –Small intestine

The exit of food from the stomach is regulated by a sphincter muscle which releases it in small amounts into the small intestine. From the stomach, the food now enters the small intestine.

Small intestine  is the longest part of the alimentary canal which is fitted into a compact space because of extensive coiling .

The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine .