Correct option (a) test cross
Explanation
In genetics, a test cross, first introduced by Gregor J Mendel, is used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait.
More simply, test cross determines the genotype Of an individual with a dominant phenotype. In some sources, the test cross is defined as being a type of back cross between the recessive homozyggte and F1-generation.