Question

intelligence testing - origins
what is the concept of mental age used for?
to approximate the age indicated by physical fitness and overall health

to approximate the age at which certain skills should be acquired

to approximate life expectancy

Explanation:

Mental age is a concept in intelligence testing (related to psychology, a subfield of Social Science) that measures the level of cognitive abilities (skills like reasoning, problem - solving) a person has, and it is used to approximate the age - level at which certain cognitive or developmental skills should be acquired. The first option is about physical fitness/health, which is not related to mental age. The third option about life expectancy is also not related to mental age as mental age focuses on cognitive development, not lifespan.

Answer:

to approximate the age at which certain skills should be acquired