Answer:
The correct answer would be allele.
An allele is defined as the alternate forms of the gene.
Usually, human contains two forms of genes which are called alleles. One form is inherited from the father and another allele is inherited from the mother.
Different alleles of gene codes for the different trait of a character.
For example, T and t are two alleles of the gene that codes for the tallness of the plant. T codes for the tallness and t codes for the short phenotype.