One parent has curly hair, the other has straight hair, and their child has wavy hair. this is an example of

a. incomplete dominance.
b. polygenic inheritance.
c. codominance.
d. multiple allele traits.

The correct answer is- A) Incomplete dominance.

Incomplete dominance means neither of the allele ( that is dominant and recessive allele) shows its phenotype complelety. In other words, no allele is completely dominant and a heterozygous condition produces an intermediate phenotype that lies between a dominant and a recessive trait.

As per the question, the phenotype of parents are - curly hair and straight hair.

As child expresses and intermediate phenotype that is wavy hair, therefore it is an example of incomplete dominance.      

the answers are a and c