## Core Concept
The frontal sinuses are a pair of paranasal sinuses located in the frontal bone, above the eyebrows. They play a role in reducing the weight of the skull and in the resonance of the voice. The frontal sinuses are typically pneumatized by the anterior ethmoidal cells.

## Why the Correct Answer is Right
The correct statement regarding frontal sinuses needs to be identified based on the provided options. However, since the options are not specified, we will proceed with general knowledge about frontal sinuses. Typically, frontal sinuses are present at birth but are not visible on X-rays until around 6 years of age, and they become more evident around puberty.

## Why Each Wrong Option is Incorrect
Without specific options provided, we can still discuss common misconceptions:
- **Option A:** If a statement claims frontal sinuses are always present, it could be incorrect because there is anatomical variation, and some individuals may have underdeveloped or aplastic frontal sinuses.
- **Option B:** If a statement suggests frontal sinuses are visible at birth on X-ray, it would be incorrect because they are not visible until later.
- **Option C:** If a statement claims frontal sinuses drain into the nasal cavity through a specific route, it could be correct or incorrect depending on the specifics; they typically drain through the frontonasal duct into the nasal cavity.
- **Option D:** Without specifics, if a statement about size, drainage, or development is incorrect based on anatomical or physiological facts, it would be wrong.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the frontal sinuses are not present at birth and become visible on X-rays around 6 years of age. Their development and pneumatization continue into adolescence. Another important clinical correlation is that the frontal sinuses are often involved in sinusitis, which can lead to significant morbidity if not properly treated.

## Correct Answer: D. Not specified.