In the family tree below, people with the recessive trait of attached earlobes
are shaded gray.
what must be true about the person labeled "a"?

C. It is a male with atleast one dominant allele

Explanation:

In the given pedigree, the two normal parents of the generation I have one daughter with the attached earlobe. Since the trait is recessive, the daughter should be homozygous recessive to express the trait. The genotype of the daughter (shaded circle in generation II) is "aa". To have a daughter with "aa" genotype, both the parents should have one copy of "a" allele. So, the genotype of both parents is "Aa".

In generation II, individual A is non-shaded square. Squares represent males in a pedigree. Since its not shaded, it does not have attached earlobe. Both the parents are heterozygous dominant for attached earlobes (Aa x Aa = 1/4 AA : 1/2 Aa : 1/4 aa). The genotype of this individual may be AA or Aa.

50% lit on the left side