Naturalists are most likely to begin breeding them in captivity (A).
The rationale behind this decision, as stated in the text, is that "the loss of one species can affect a whole ecosystem." This is the reason why the naturalists in question took these measures in the case of the California condor, and their argument indicates that they would do it again for another species if it meant they would preserve the ecosystem.
By capturing some of the few leftover individuals of a species, you make it easier for the males and females to find themselves and produce offspring, which can grow up in safe conditions and later be released into the wild.