A positive or negative evaluation of an object of thought defines

A) an attitude.
B) an opinion.
C) a schema.
D) a preference.

An attitude is a positive or negative evaluation of an object of thought, which can influence our behavior towards it. Option B is also a possible answer, but an opinion is a more general expression of one's beliefs or views on a particular topic, while an attitude is more specific to an object or situation. Option C refers to a mental framework or structure that helps us organize and interpret information, but it does not necessarily involve an evaluation. Option D refers to a particular liking or inclination towards something, which may or may not involve a positive or negative evaluation.