Compared to Informal Observation, What Is an Advantage of Formal

Compared to informal observation, what is an advantage of formal observation?

A) Formal observations provide more perspective because they are written after an open-ended, out-of-office interview in a non-clinical setting.
B) Formal observations rarely require the use of naturalistic settings.
C) Formal observations are more reliable due to the focus on behaviours that are both observable and measurable.
D) Formal observations give more information about an individual because they require a three-hour minimum time commitment.