Why did gregor mendel choose to use purebred plants in his experiments?

Gregor Mendel chose to use purebred plant is his experiments enabled him to focus on the relationship between hybrid plants. He is considered the father of genetics today. 
Gregor Mendel was born on July 22, 1822, in a small farming town in Czechoslovakia. His natural interest in science and hereditary science led him to start his experiments with the pea plant. He chose the pea plant because he needed parental plants which had constant and differentiating characteristics. He first tested a plant's ability to propagate non-hybrid family lines. He discovered that the pea plant produced family lines with the most consistent characteristics. 

The correct answer is b