The correct options are
A Stereotypes are problematic because they are unjustified opinions.
B Stereotypes are problematic because they are over-simplified opinions.
C Stereotypes are problematic because they ignore diversity among individuals.
Stereotypes are problematic because they are an over-simplified and unjustified opinion that ignores diversity among individuals. It hampers appreciation for diversity and ignores difference as it does not appreciate the uniqueness of individuals.