In Pea Plants, the Allele for Round Peas (R) Is

In pea plants, the allele for round peas (R) is dominant to the allele for wrinkled peas (r) .A gardener has a plant he got from his neighbor that produces round peas, but he does not know its genotype.What simple procedure could he do to determine the genotype of his new plant?

A) Perform a dihybrid cross-if only 1 out of 16 offspring are wrinkled, then the new plant's genotype is RR.
B) Perform a test cross with a plant that has wrinkled peas-if any offspring give wrinkled peas, then the new plant's genotype is Rr.
C) Perform a test cross with a plant that has an Rr genotype-if all of the offspring give round seeds, then the new plant's genotype is Rr.