You are answering a USMLE-style medical question. Question: A 3-year-old boy is brought to his pediatrician for evaluation because his parents have been concerned by a number of troubling signs. Specifically, they have noticed that he has been exhibiting aggressive behavior as well as hyperactivity. In addition, he has had intellectual disability and is slow to hit developmental milestones. Physical exam reveals coarse facies, short stature, and joint stiffness. Eye exam reveals no abnormalities of the cornea or lens. Based on these findings, the patient is referred to a geneticist for further evaluation. Which of the following substances would most likely accumulate in the cells of this patient? Options: A) Cerebroside sulfate B) Galactocerebroside C) Heparan sulfate D) Sphingomyelin Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.