Which are different forms of the same gene?
genotypes
phenotypes
alleles
traits

Option C, Allele

Explanation:

Alleles are the form of same gene. There are minute variations in the DNA structure of the alleles.  

Genotype is basically the set to two alleles (which may be same or different from each other) which shall define the phenotype of the species.  Hence both genotype and phenotype cannot be the correct answer.

Traits is the characteristics associated with alleles thus it is also not the correct answer

Hence Option C , Allele is the right answer

An example of allele is

The height is represented by the allele T and t

Where "T" means alleles expressing tall people

and "t" means alleles expressing short people

Though the trait associated with alleles "T" and "t" are different , they represents the same gene i.e the gene associated with height.

answer; i believe that the correct answer is (light);

i think its the first one