Answer is gizzard because it possess chitinuous teeth like projection which helps in grinding and crushing food while feeding.gizzard is the hardest part too.

The correct answer is option 'B' - Gizzard.

The alimentary canal of an earthworm is a long, muscular tube that runs from its mouth to its anus and is responsible for the digestion and absorption of nutrients. The alimentary canal is made up of several distinct regions, each with its own unique structure and function.

The innermost layer of the alimentary canal is called the mucosa, which is made up of epithelial cells that secrete mucus to lubricate the passage of food. Surrounding the mucosa is the submucosa, which contains blood vessels, nerves, and connective tissue. The next layer is the muscularis externa, which consists of two layers of smooth muscle that contract and relax to propel food through the digestive tract. The outermost layer is the serosa, which is a thin, protective layer of connective tissue.

The inner cuticle layer, also known as the typhlosole, is a unique structure found in the intestine of the earthworm. The typhlosole is a fold of the intestinal wall that increases the surface area for absorption of nutrients. It is lined with a thick layer of cuticle, which is a tough, flexible material that protects the underlying tissues from mechanical damage.

Among the given options, the gizzard is the region of the earthworm's alimentary canal where the inner cuticle layer is present. The gizzard is a muscular organ that acts as a grinding chamber, breaking down food particles into smaller pieces. The inner cuticle layer in the gizzard helps to protect the underlying tissues from the abrasive action of the food particles.

The other options mentioned - pharynx, stomach, and intestine - do not have the inner cuticle layer. The pharynx is the region responsible for the ingestion of food, the stomach is responsible for the initial breakdown of food through the action of enzymes and acid, and the intestine is responsible for the absorption of nutrients. While these regions may have other specialized structures, they do not have the inner cuticle layer found in the gizzard.

In conclusion, the inner cuticle layer is present in the alimentary canal of an earthworm in the gizzard. The gizzard is a specialized region that helps in the mechanical breakdown of food, and the inner cuticle layer protects the underlying tissues from damage.