In Correlation, the connection between two or more events of things are checked. In a correlation study, a researcher find out the relationship between naturally occurring variables.
So here a researcher wants to check out the relationship between two naturally occurring variables which is a person's birth order and it's leadership ability so it is an example of a correlation study.
Alfred Adler is the 20th century did this study and found that the person's birth order impacts the person's personality. So the right answer is b.
