Jennifer Believes That Mark, a New Employee, Is the Most

Jennifer believes that Mark, a new employee, is the most efficient employee in the company. Her basis of this opinion is that Mark was polite and had once helped her find her car keys which she had misplaced in the office. Now, whenever she sees Mark working in the office, she assumes that he is the hardest working employee in the company. Jennifer's belief is an example of the

A) halo effect.
B) hindsight bias.
C) placebo effect.
D) courtesy bias.