In a Particular Plant,leaf Color Is Controlled by Gene Locus

In a particular plant,leaf color is controlled by gene locus D.Plants with at least one D allele have dark green leaves,and plants with the homozygous recessive dd genotype have light green leaves.A true-breeding dark-leaved plant is crossed with a light-leaved one,and the F₁ offspring is allowed to self-pollinate.The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure above,where 1,2,3,and 4 represent the genotypes corresponding to each box within the square.Which of the boxes correspond(s) to plants with a heterozygous genotype?

A) 1 only
B) 1 and 2
C) 2,and 3
D) 1,2 and 3