**Core Concept**
The child's presentation of mental retardation, blond hair, and convulsions at 1 year of age suggests a disorder of fatty acid metabolism, specifically a defect in the beta-oxidation of very long-chain fatty acids. This condition is characterized by the accumulation of very long-chain fatty acids in tissues, leading to cellular dysfunction.

**Why the Correct Answer is Right**
The correct diagnosis is **Zellweger syndrome**, a peroxisomal biogenesis disorder caused by mutations in the PEX genes. This leads to a deficiency of peroxisomal enzymes, including those involved in the beta-oxidation of very long-chain fatty acids. The resulting accumulation of these fatty acids in tissues causes cellular dysfunction, manifesting as mental retardation, blond hair (due to the lack of melanin), and convulsions. The clinical presentation is consistent with a disorder of fatty acid metabolism, and the genetic basis of Zellweger syndrome explains the biochemical abnormalities.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely to be a distractor related to another disorder of fatty acid metabolism, such as carnitine palmitoyltransferase (CPT) deficiency. However, CPT deficiency typically presents with episodes of hypoketotic hypoglycemia and does not typically cause blond hair.
* **Option B:** This option may be a distractor related to a disorder of amino acid metabolism, such as phenylketonuria. However, phenylketonuria does not typically cause blond hair or convulsions.
* **Option C:** This option may be a distractor related to a disorder of carbohydrate metabolism, such as galactosemia. However, galactosemia does not typically cause blond hair or convulsions.

**Clinical Pearl / High-Yield Fact**
Zellweger syndrome is a rare disorder that highlights the importance of peroxisomal function in human health. Peroxisomes are organelles involved in the breakdown of fatty acids and amino acids, and defects in peroxisomal biogenesis can lead to a range of clinical disorders.

**Correct Answer:** B.