Which of the Following Statements Concerning Personal Observation Is Most

Which of the following statements concerning personal observation is most accurate?

A) Personal observation is the most accurate because the observer is able to pick up subtleties in the respondent's body language, speech patterns, and facial movements that are often missed by other data collection methods.
B) Personal observation is especially suited for small up-and-coming businesses that need the research data but cannot yet afford to hire professional marketing companies.
C) Personal observation is very effective since it can reveal not only what people do, it can effectively determine why they do it.
D) Personal observation is both useful and flexible but it can be costly and unreliable when different researchers interpret the same data in different ways.
E) Personal observation has the benefit of observing and comparing two different behaviors in the same subject because people often change their behavior if they know they are being studied.