Humans Have a Gene, T, That Is Involved in Muscle

Multiple Choice

Humans have a gene, T, that is involved in muscle formation of the tongue. Individuals homozygous for one allele can roll their tongues, while individuals homozygous for the other allele cannot. If both parents can roll their tongues, but their child cannot, what can be said about the mode of inheritance?

A) Tongue rolling is dominant.
B) Tongue rolling is recessive.
C) The parents were both homozygous, but the child was heterozygous.
D) Tongue rolling is dominant, and both parents were heterozygous (Tt) .
E) Tongue rolling is recessive, and both parents were heterozygous (Tt) .