Concept:Mental age is a measure of intellectual development compared to the average ability at a given chronological age. It was first introduced by French psychologist Alfred Binet.Explanation:Alfred Binet defined mental age to describe a child's intellectual performance relative to their actual age. He, along with Theodore Simon, created the first intelligence test in 1905. Mental age forms the basis for calculating Intelligence Quotient (IQ), though the term IQ was coined by William Stern. The formula is: IQ=CAMA​×100. Later, Lewis Terman revised Binet’s test into the Stanford-Binet test, and Cyril Burt contributed to educational quotient research. However, the concept of mental age itself originated with Binet.Answer:A. Binet