Lilly Is a Researcher Who Wants to Know How Often

Lilly is a researcher who wants to know how often high-school students are using their cell phones to cheat on tests.Lilly pretends to be a visiting student.She sits in on classes and observes students as they take tests.Lilly's method of research is known as

A) in situ research.
B) naturalistic observation.
C) covert research.
D) in vivo research.