(a) When Mendel cross pollinated pure tall pea plants with pure dwarf pea plants, only tall plants were obtained in $F_1$ generation in 3:1 ratio. Thus appearence of tall character in both $F_1$ and $F_2$ shows that it is a dominant character. The absence of dwarf in $F_1$ generation reappears in $F_2$ shows dwarfness in the recessive character. (b) When Mendel conducted a dihybrid cross having two sets of characters, he obtained only one set of parental characters in $F_1$ generation where as in $F_2$ generation he obtained both the set of parental characters as 9:3:3:1 ratio. Thus appearance of new generation or recombinants in the $F_2$ generation along with parental type shows that traits are inherited independently.