## Core Concept
Fetal alcohol syndrome (FAS) is a condition characterized by a set of physical, behavioral, and cognitive abnormalities that occur in individuals whose mothers consumed alcohol during pregnancy. The dysmorphic facial features are a key component of the diagnosis. These features are often remembered by the acronym **"A" for short palpebral fissures, "B" for a smooth philtrum, and "C" for a thin vermilion border**.

## Why the Correct Answer is Right
The correct answer is associated with the understanding that the characteristic facial features of fetal alcohol syndrome include **short palpebral fissures (A)**, a **smooth philtrum (B)**, and a **thin vermilion border of the upper lip (D)**. These are well-documented and commonly accepted criteria.

## Why Each Wrong Option is Incorrect
- **Option A:** Short palpebral fissures are indeed a feature of FAS, making this option incorrect as an "except" choice.
- **Option B:** A smooth philtrum is also a characteristic feature, which makes this option incorrect.
- **Option D:** A thin vermilion border of the upper lip is another recognized feature, which makes this option incorrect.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that not all individuals with FAS will have all three facial features, but the presence of at least two is often considered significant. Additionally, the diagnosis of FAS requires documentation of **prenatal alcohol exposure**, **dysmorphic facial features**, and **neurodevelopmental or functional abnormalities**.

## Correct Answer: C.