$F_1$ generation Mendel pollinated a pure-breeding tall plant with a pure-breeding dwarf plant. But for getting the $F_2$ generation,he simply self-pollinated the tall $F_1$ plants. Why?

• A
  To maintain the purity of the tall trait.
• B
  To observe the segregation of alleles and the reappearance of the recessive trait.
• C
  Because cross-pollination was not possible for the $F_2$ generation.
• D
  To produce more seeds for the experiment.