Final answer:
Cliff likely has an intellectual disability due to his low IQ and issues with adaptive behaviors. However, his extraordinary music replication skill points towards 'savant' abilities, demonstrating the nuanced spectrum of intellect and cognitive abilities.
Step-by-step explanation:
The statement that best describes Cliff, an adult with an IQ of 50 who can replicate any piece of music on his piano after only hearing it once, indicates that he may have an intellectual disability along with a remarkable musical ability. Intellectual disabilities are characterized by an IQ approximately two standard deviations below the mean, which is around 70 on a standard IQ test, and significant difficulties with adaptive behaviors evident before the age of 18. Cliff's impressive musical talent, however, is reminiscent of 'savant' abilities often found in individuals with developmental disorders. This combination of intellectual disability and exceptional skill can occasionally occur, illustrating the complex nature of cognitive abilities and intelligence.