Who studied inheritance of traits in pea plants? Why did he select the pea plant? Which trait gets expressed in the first generation? In what ratio,traits with two contrasting characters get expressed in the second generation?

(D) Gregor Johann Mendel studied the inheritance of traits in pea plants.
He selected the pea plant because it possesses several contrasting visible characters such as round/wrinkled seeds,tall/short plants,and white/violet flowers. Furthermore,pea plants are easy to cultivate and have a short life cycle.
Only the dominant traits are expressed in the first generation ($F_1$ generation).
In the second generation ($F_2$ generation) of a dihybrid cross,the traits with two contrasting characters are expressed in the ratio of $9: 3: 3: 1$.