Which Statement Is an Example of a Demand Characteristic in Everyday

Which statement is an example of a demand characteristic in everyday life?

A) Self-report measures of everyday mood tend to fluctuate unsystematically.
B) People tend to evaluate physically attractive strangers as more positive on a plethora of dimensions than less attractive strangers.
C) University students who receive good grades in a course tend to rate that course higher than do students who receive low grades in the course.
D) Schoolchildren are much less rowdy on the bus after a noticeable video camera is mounted in the front of the bus.