Okay, let's tackle this question. The user is asking which of the options is an X-linked mucopolysaccharidosis. First, I need to recall what mucopolysaccharidoses (MPS) are. They're a group of lysosomal storage disorders caused by enzyme deficiencies that lead to the accumulation of glycosaminoglycans (GAGs). These are inherited in an autosomal recessive or X-linked manner.

Now, the question is specifically about X-linked types. I remember that most MPS are autosomal recessive, but a few are X-linked. Let me think: MPS I is Hurler syndrome, autosomal. MPS II is Hunter syndrome, which is X-linked. Then there's MPS III (Sanfilippo), IV (Morquio), VI (Maroteaux-Lamy), VII (Sly), and IX. Among these, Hunter (MPS II) is X-linked recessive because the deficient enzyme is iduronate-2-sulfatase, which is on the X chromosome. So the correct answer should be Hunter syndrome.

Looking at the options, the user didn't provide them, but the correct answer is likely B if Hunter is an option. The other options would be other MPS types that are autosomal. For example, Hurler is autosomal recessive. The clinical pearl here is that X-linked inheritance affects males more severely and is passed from carrier females. So the key is to remember which MPS types are X-linked versus autosomal.

**Core Concept**
Mucopolysaccharidoses (MPS) are lysosomal storage disorders caused by deficiencies in enzymes degrading glycosaminoglycans (GAGs). X-linked inheritance occurs in **Hunter syndrome (MPS II)**, caused by deficiency of iduronate-2-sulfatase. Other MPS types are autosomal recessive.

**Why the Correct Answer is Right**
**Hunter syndrome (MPS II)** is the only X-linked mucopolysaccharidosis. It results from mutations in the *IDS* gene on the X chromosome, encoding iduronate-2-sulfatase. This enzyme deficiency leads to accumulation of dermatan sulfate and heparan sulfate, causing progressive multisystem disease with intellectual disability, coarse facial features, and skeletal abnormalities.

**Why Each Wrong Option is Incorrect**
**Option A:** *Hurler syndrome (MPS I)* is autosomal recessive, caused by alpha-L-iduronidase deficiency.
**Option C:** *Morquio syndrome (MPS IV)* is autosomal recessive, due to deficiency of galactose-6-sulfate sulfatase.
**Option D:** *Sanfilippo syndrome (MPS III)* is autosomal recessive, involving heparan sulfate metabolism defects.

**Clinical Pearl / High-Yield Fact**
X-linked recessive disorders like Hunter syndrome predominantly affect males and are transmitted by carrier females. Remember the mnemonics **"HURLER" (I), "HUNTER" (II), "MORQUIO" (IV)** for autosomal recessive types, while **"HUNTER" (II)** stands out as X-linked.

**Correct Answer: B. Hunter syndrome**

✓ Correct Answer: B. Hunter's syndrome