The correct answer is: B. belief
A belief is an acceptance that something is true or real, especially one without proof. In this case, the belief is that all man-eaters are old and mangy. This belief is not based on evidence, but rather on a stereotype. There is no evidence to suggest that all man-eaters are old and mangy. In fact, there are many cases of man-eaters that are young and healthy.
An observation is a statement about something that has been seen or experienced. In this case, the observation would be that some man-eaters are old and mangy. However, this observation does not support the belief that all man-eaters are old and mangy.
A fact is a statement that is true or can be proven to be true. In this case, there is no fact to support the belief that all man-eaters are old and mangy.
An illusion is a false or misleading perception of something. In this case, the illusion would be that all man-eaters are old and mangy. However, this illusion is not based on reality.