In cockroach, the common duct of the salivary reservoir opens the base of ______
A. Pharynx
B. Maxilla
C. Mandible
D. Hypopharynx

Hint: To find the correct answer, one should know about the anatomy of the cockroach. Cockroaches are insects. There are a total of 4600 species of cockroaches known to date. Among 4600, only 30 species of cockroaches are associated with human habitats. They have two salivary glands.

Complete answer:
Let’s talk about the anatomy of the digestive tract of cockroaches. The head region of cockroaches has parts such as labium, maxilla, eye, mandible, labrum, ocellus, etc. The alimentary canal can be divided into three parts such as foregut, midgut, and hindgut. The mouth opens into a short tubular pharynx which leads to the narrow tubular passage called the esophagus. This esophagus opens into a sac-like structure called crop which is being used for storing food. The crop further leads to a gizzard that is being used to grind food particles. The entire foregut is lined with cuticles. This further leads to hepatic caeca which produce digestive enzymes.
Now let’s talk about the salivary gland present in the mouth. The common duct of the salivary gland opens at the base of the hypopharynx. Hypopharynx is a structure hanging between mouthparts being used to mix saliva.

So the correct answer is D, hypopharynx.

Note:
The salivary glands are present in the pairs. They are located on either side of the crop. These glands are made of the glandular part as a reservoir. The reservoir is located at connecting tissues of salivary glands and remains connected through a duct. The salivary glands contain hexagonal glandular cells and they open into a small narrow duct.