The Most Serious Disadvantage of Observation Is

The most serious disadvantage of observation is .

A) observational data is often time consuming and expensive, and it is difficult to observe certain forms of behavior, such as personal activities.
B) the reasons for the observed behavior may not be determined because little is known about the underlying motives, beliefs, attitudes, and preferences.
C) observational methods permit measurement of actual behavior rather than reports of intended or preferred behavior.
D) if the observed phenomenon occurs frequently or is of short duration, observational methods may be cheaper and faster than survey methods.