Which statement best describes the relationship between an allele and a

Option B

Explanation:

An allele is considered as a variant form of a gene. A single gene possess various forms and these all forms are located at the same gene locus. The different phenotype of a gene is due to varied combination of alleles.  

For example – let “T” represents the allele for tall gene and “t” represents the allele for short gene and “T” is dominant over “t”. Genotype “TT” or “Tt”  represents a tall species and genotype “tt” represents a short species.

Hence, option B is correct