Prospective Study- Stem in a Prospective Study of Development,researchers Use

Prospective study- stem In a prospective study of development,researchers use which type of approach?

A) Compare people at one time who did and did not experience a major life transition.
B) Track participants before and after they experience a major life transition.
C) Ask participants to recall what they were like when they were younger.
D) Interview close friends and relatives of participants over several time points.