**Core Concept**
A mucocele is a mucus-containing, distended, and often inflamed or infected sinus cavity or air cell. It is usually a result of the blockage of the sinus ostium, leading to the accumulation of mucus and possible infection. This condition can be caused by various factors such as anatomical abnormalities, trauma, or tumors.

**Why the Correct Answer is Right**
The frontal, ethmoid, and sphenoid sinuses are most commonly affected by mucoceles due to their relatively smaller size and narrower drainage pathways. The frontal recess, a critical area for drainage of the frontal sinus, is particularly prone to becoming blocked, leading to the formation of a mucocele. The accumulation of mucus in these sinuses can cause significant inflammation and may lead to complications such as orbital or intracranial extension.

**Why Each Wrong Option is Incorrect**
**Option A:** The maxillary sinus is the largest of the paranasal sinuses but is less commonly affected by mucoceles due to its relatively larger size and more robust drainage pathways.
**Option B:** Although the lacrimal sac can become obstructed and form a mucocele, this is a relatively rare occurrence and not as commonly associated with sinus mucoceles as the frontal, ethmoid, or sphenoid sinuses.
**Option C:** The nasal cavity itself is not typically a site for mucocele formation, as the nasal passages are generally larger and have more robust drainage.

**Clinical Pearl / High-Yield Fact**
A mucocele can be a sign of an underlying anatomical abnormality, such as a congenital defect or a tumor, which may require further investigation and intervention.

**Correct Answer: D. Frontal sinus.**