Which of these statements is incorrect?

• A
  Incomplete dominance is a phenomenon where one allele masks the expression of another allele in heterozygous individuals.
• B
  In a cross between true-breeding red-flowered $(RR)$ and true-breeding white-flowered plants $(rr)$ of snapdragon,the $F_1$ generation will be pink $(Rr).$
• C
  Dominance is a phenomenon where one allele masks the expression of another allele in heterozygous individuals.
• D
  $A$ recessive allele may produce a non-functional enzyme or no enzyme at all.