Compare and contrast codominance and incomplete dominance.

Co dominance is when the offspring inherits the trait of the mother and of the father. Like a black cat and a white cat's offspring will be a spotted black cat with maybe white spots.
Incomplete dominance is when both of the traits are combined. Like when the offspring of a red flower and a white flower will give you a pink flower.
However, both co dominance and incomplete dominance are results of mixed traits.
Hope this helps. 

The correct answer for the fill in the blank is- C) Racism.

Racism is a system of belief ( doctrine), which indicates that the characteristics and capacities of human beings can be determined through their race ( that includes physical traits, culture and traditions, ethnicity).

Racism produces difference among races by indicating some superior and others as inferior race.

Therefore, C) is the right answer.