What is a study where you try to observe subjects in a natural environment

Isabel wants to sign up with the online social network teenbook, which she heard about from her friends at school.the teenbook site asked isabel for some personal information to complete her registration.in addition to her full name, teenbook asked for the name of her school, the city where she lives, her age, and her favorite foods.what is the only information that isabel should give to best ensure her safety?