What does it mean if there are two different alleles for a trait.

A. The trait is always homozygous

B. That trait is the same for everyone

C. The trait could show up in two different forms

D. There are a total of two possible genotypes for that trait

Option C

Explanation:

If a trait is represented by two different alleles then genotype for such trait would be heterozygous. A homozygous genotype has same alleles for a given trait. Thus, option A is correct.

Now this heterozygous can express in three different forms - a) it can express the trait of dominant allele, b) it can express co-dominance, and c) it can express incomplete dominance. Thus, option C is correct. One form will be the form where the dominant allele will express in a homozygous genotype and the other form will be any of the three options given above.