Mr Agu Mohammed is a 20-year-old young man with an oropharyngeal mass bulging from the nasopharynx. He alleges to have loss of hearing in both ears. He is diagnosed with antrochoanal polyps. These polyps emanate from the .......... sinus.

Antrochoanal polyps (ACPs) are a specific type of benign nasal polyp. They are characterized by their origin and extension. The term "antro-" refers to the maxillary antrum, which is another name for the maxillary sinus.

ACPs typically originate from the maxillary sinus, grow into the nasal cavity through the ostium, and then extend backward into the choana (the posterior opening of the nasal cavity) and often into the nasopharynx and oropharynx.

• a. Ethmoid: Ethmoid polyps are common but usually originate from the ethmoid sinuses and are often multiple. They are not typically referred to as antrochoanal polyps.
• b. Maxillary: This is the correct origin for antrochoanal polyps, as indicated by the "antro-" prefix.
• c. Frontal: Frontal sinus polyps are less common and do not typically present as antrochoanal polyps.

The final answer is $\text{b. Maxillary.}$