Answer:
phenotype.
Step-by-step explanation:
Mendel is known as father of genetics. Genotype may be defined as the genetic constitution of an organism whereas phenotype may be defined as the physical constitution of an individual.
When Mendel performed the dihybrid cross ( two distinguish characters at a time), he obtained the phenotype ratio of 9:3:3:1. These two traits can assort independently and follows the Mendel law.
Thus, the correct answer is option (a).