The correct option is A One
In a diploid organism, chromosomes are present in pairs known as the homologous pairs of chromosomes.
Alleles are alternative forms of the same gene located at the same loci on the homologous pair of chromosomes.
An individual possesses only two alleles of a gene, while the gametes carry a single allele of a particular gene.
Hence, each chromosome carries one allele of a gene in a diploid individual.