Based on the following pedigree, how is the trait being inherited?

A. sex-linked inheritance
B. complete dominance
C. codominance
D. multiple alleles

The correct answer is option B. "complete dominance".

Explanation:

Widow's peak is a trait characterized by the growth of a hairline in the center of the forehead. By looking at the pedigree we can conclude that widow's peak has no sex-linked inheritance because there is father-to-son transmission. There is no codominance or multiple alleles inheritance neither, because there is no slight differences in the trait (people either have or not have widow's peak). We can conclude that widow's peak have a complete dominance inheritance, because in the case where both parents have widow's peak they have a female daughter with no widow's peak. This means that both parents were  heterozygous of the widow's peak allele, and since both expressed the trait we can conclude that it is completely dominant.