**Core Concept**
A chalazion is a type of lid cyst resulting from the blockage of a meibomian gland in the eyelid, leading to inflammation and granulomatous reaction.

**Why the Correct Answer is Right**
Chalazion occurs due to the accumulation of sebum and cellular debris within the meibomian gland, which triggers an inflammatory response and granuloma formation. The meibomian glands are apocrine glands located in the tarsal plate of the eyelid, responsible for producing meibum, a type of sebum that helps to lubricate the eye. The blockage of these glands leads to the formation of a chalazion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the pathophysiology of a chalazion.
**Option B:** This option is incorrect as it does not specify the anatomical location of the blockage, which is crucial for understanding the development of a chalazion.
**Option C:** This option is incorrect as it describes a different type of lid cyst, such as a hordeolum externum or internum, which is caused by bacterial infection.

**Clinical Pearl / High-Yield Fact**
A chalazion is often confused with a hordeolum, but the key difference lies in the location of the blockage: meibomian gland for chalazion and sebaceous gland for hordeolum.

**Correct Answer: D. Meibomian gland blockage.**