Genes which generally code for a pair of contrasting traits are known as _________ .

The correct option is B alleles

Alleles are a pair of contrasting traits of a character that are coded by a gene.

Character is any feature that is observable. It can be inherited from parents or acquired by one during their lifetime. Although inherited characters are affected by genes, acquired ones are affected by the environment.

A true breeding line or variety is one where the offspring have the same traits as the parents. This is when a species has undergone continuous self-pollination generation after generation showing stable trait inheritance and expressions for several generations.