Longitudinal Studies of Intellectual Abilities Were Conducted on About 5,000

Longitudinal studies of intellectual abilities were conducted on about 5,000 people in Seattle over the past 50 years.Which of the following was a conclusion drawn from the study?

A) General intellectual abilities gradually increase until the early 40s and then remain fairly stable until the mid-60s.
B) General intellectual abilities gradually increase after the early 40s till the mid 60s and then remain fairly stable until the late-70s.
C) There is an increase in general intellectual abilities up to the early 40s and thereafter it starts decreasing rapidly.
D) General intellectual abilities keep increasing with age and is at the highest during the time of death.