The correct answer is option B, that is, genes are the basic unit of information affecting a genetic trait.
A gene refers to the fundamental functional and physical unit of heredity. Genes are formed of deoxyribonucleic acids. Some of the genes work as directions to produce molecules known as proteins, while numerous of the genes do not code for proteins. The genes, in humans, differ in size from a few hundred of DNA bases to more than two million bases.