Purple Flower ( a )Is Dominant Over White Flower

Multiple Choice

Purple flower ( A ) is dominant over white flower ( a ) , and tall stem ( B ) is dominant over short stem ( b ) . The Punnett square represents a cross between two dihybrids ( AaBb   ´   AaBb ) .
In the figure above, how many plants would have the genotype AaBb ?

A) 1
B) 3
C) 4
D) 6
E) 9