Gregor Mendel concluded from his pea plant experiments that each plant had two factors (or alleles) that controlled each of its traits, and that this was the reason there were two different forms of each characteristic he studied. Which observation supports this conclusion?

A. Each offspring from the test crosses had one of the two parental forms of the characteristic under investigation.

B. One-half of the second-generation plants produced both forms of the characteristic being studied on the same plant.

C. One-fourth of the second-generation plants produced only offspring with the recessive form of each characteristic.

D. All of the hybrids produced from the first cross had the dominant form of the characteristic being studied.​