The correct answer is option C) pharyngeal wall.

The salivary glands in an earthworm are found in the pharyngeal wall. The pharynx is a muscular tube located in the anterior region of the earthworm's digestive system, just behind the mouth or buccal cavity. The pharyngeal wall contains several pairs of salivary glands that secrete saliva into the buccal cavity.

Salivary glands play an important role in the digestion process of earthworms. The saliva secreted by these glands helps in lubricating the food and breaking it down into smaller particles. It contains enzymes that initiate the process of chemical digestion.

Saliva in earthworms contains enzymes like amylase, which helps in the digestion of carbohydrates. The amylase breaks down complex carbohydrates into simpler sugars that can be easily absorbed by the earthworm's digestive system. This enzymatic action of saliva aids in the overall digestion and absorption of nutrients.

The salivary glands in earthworms are located in the pharyngeal wall for efficient secretion and delivery of saliva into the buccal cavity. The buccal cavity is the initial part of the earthworm's digestive system where food enters. The secreted saliva mixes with the ingested food, forming a moist ball or bolus, which is then passed to the esophagus for further digestion and absorption.

In conclusion, the salivary glands in earthworms are found in the pharyngeal wall, and their secretions play a crucial role in the digestion and absorption of nutrients.

The dorsal chamber is also called salivary chamber which contains pharyngeal gland that is composed of many chromophil cells. Dorsally pharyngeal gland is lined by villi. The chromophil cells produce saliva containing proteolytic enzymes and mucin. Mucin makes the food soft and protease converts protein into an amino acid. The ventral chamber is a conducting chamber which conducts digested or undigested food material from the pharynx to the oesophagus.
So the correct answer is 'Pharyngeal wall'.