Consider a cross between true-breeding round and true-breeding wrinkled pea plants, to produce F1 heterozygotes. If F1 heterozygotes are then self-crossed, which statement is TRUE of the F2 plants?

a. If all of the F2 round-pea plants are testcrossed, one-third of the offspring will be round.

b. For any F2 round-pea plant that is self-crossed, there is a one-half chance the offspring are round.

c. If all of the F2 round-pea plants are testcrossed, one-ninth of the offspring will be round.

d. If all of the F2 round-pea plants are testcrossed, two-thirds of the offspring will be round.