Answer:
WWDD, WwDd, WWDd or WwDD
Step-by-step explanation:
Given that wavy and dark hair is dominant over straight and red hair. A male with dark wavy hair has mother with recessive straight red hair so her genotype is definitely wwdd.
The son will get recessive alleles "w" and "d" from his mother. But he shows dominant phenotype which means that his father gave him the dominant alleles "W" and "D". Hence his father can have WWDD, WwDd, WWDd or WwDD genotype.