Concept:Understanding the relationship between chronological age and mental age to determine intelligence quotient.Explanation:Chronological age (CA) is the actual age of a person since birth. Mental age (MA) is the age at which a person's intellectual abilities are at. The Intelligence Quotient (IQ) is calculated as $IQ = \frac{MA}{CA} \times 100$.Raheem is 12 years old, so his chronological age is $CA = 12$ years.He has passed Class X with good grades. This indicates that his intellectual abilities are advanced for his age.If someone performs well on tests designed for older age groups, their mental age is considered higher than their chronological age.Since Raheem passed Class X with good grades at the age of 12, it implies his mental capabilities are equivalent to or greater than those of someone older than 12. Therefore, his mental age is likely higher than his chronological age.Answer:A. High