Which of the Following Can Be Considered a Major Difficulty

Which of the following can be considered a major difficulty in the measurement of personality through direct observations of behavior (whether in natural or in artificial settings) ?

A) It's very time-consuming and expensive to measure many traits reliably in many persons.
B) Observers of behavior show very poor agreement (i.e. ,low inter-observer reliability) .
C) Behaviors provide little if any information about personality traits.
D) Both A and B above
E) Both A and C above