What do you know about an organism's parents if it is heterozygous for a certain trait?

A. Both parents supplied the same allele.

B. The parents supplied different alleles.

C. The parents had different traits.

D. The parents had the same traits.

No the parents do not have to be homozygous, as using a punnet square:

D = dominant characteristic

d = recessive characteristic

D d

d Dd dd

d Dd dd

Here, it is possible to have a heterozygous organism, with one heterozygous parent. The parents could be any combination except all of the same gene (both genotypes DD or dd)