The following pedigree shows the inheritance of attached earlobes (black symbols) and unattached earlobes (white symbol). Both alternative phenotypes are quite common in human populations. If the phenotypes are determined by alleles of one gene, then attached earlobes are inherited as an
a. autosomal dominant.
b. autosomal recessive.
c. X-linked dominant.
d. X-linked recessive
e. Could be more than one of the above