Select the most appropriate option to fill in the blank.
Stereotypes may be used to justify ill-founded ____________ or ignorance, and prevent people of stereotyped groups from entering or succeeding in various activities or fields.

The context of the sentence is about stereotypes and their negative consequences, such as blocking individuals from achieving success based on their identity group.
Prejudices refers to preconceived opinions that are not based on reason or actual experience. Stereotypes are naturally used to justify ill-founded prejudices.

While "conclusions" or "thoughts" could theoretically fit, "prejudices" is the precise terminology used when discussing social stereotyping and systematic exclusion.