Abiologist spends her summer break collecting frogs from a remote jungle in peru. she discovers two distinct color forms that could be variants of a single species or two different species. what would be the most direct test of their species statusunder the biological species concept?

I found the missing choices:

A. Compare the color patterns of the two groups. If they are distinct enough, the two forms belong to different species.
B. Observe mating in the natural environment of the two groups. If the two forms do not mate with each other, they are different species.
C. Compare the habitat use of the two groups. If they use different habitats, they must be different species.
D. Compare the DNA of the two groups. If their genes are different, they must be different species.

My answer is: 
B. Observe mating in the natural environment of the two groups. If the two forms do not mate with each other, they are different species.