Answer: An image about a certain group of people that you assume is true is a (C.) stereotype.
Explanation: A stereotype is a fixed image about a particular group of people, such as an ethnic group. In other words, a stereotype is a set of characteristics that are incorrectly assumed to be true and assigned to a specific group of people. In that way, in general, a stereotype is an oversimplified and, most times, inaccurate idea. For example, there are many stereotypes that surround Africans since people see all Africans as poor, unable to access to technology and likely to only listening to tribal music.