Differentiate between a monohybrid cross and a dihybrid cross.

• A
  Monohybrid cross involves one trait; Dihybrid cross involves two traits.
• B
  Monohybrid phenotypic ratio is $3$:$1$; Dihybrid phenotypic ratio is $9$:$3$:$3$:$1$.
• C
  Monohybrid genotypic ratio is $1$:$2$:$1$; Dihybrid genotypic ratio is $1$:$2$:$1$:$2$:$4$:$2$:$1$:$2$:$1$.
• D
  All of the above.