Answer
a. Dominance – When two traits (character) of a species is crossed, resulting offspring in F1 generation displays character of any one parent then it called as dominance.
b. Co-dominance – When two traits (character) of a species crossed, resulting offspring in F1 generation display characters of parents then it is called as co-dominance, e.g ABO blood group.
c. Incomplete - When two traits (character) of a species is crossed, resulting offspring in F1 generation don’t resemble either of parents so called as incomplete dominance.