Bird guides once listed the myrtle warbler and audubon’s warbler as distinct species. recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. which of the following pieces of evidence, if true, would be cause for this reclassification?
a. the two forms interbreed often in nature, and their offspring survive and reproduce well.
b. the two forms live in similar habitats and have similar food requirements.
c. the two forms have many genes in common.
d. the two forms are very similar in appearance.

a. The two forms interbreed often in nature, and their offspring survive and reproduce well.

Explanation:

A species is a group of organisms that can breed with each other and reproduce viable offsprings that are also capable of reproducing in future.

Here, Audubon's warbler and Myrtle warbler had separate habits which might or might not be similar. Their food requirements also might or might not be similar. But they were found to interbreed and give rise to offsprings who survived and reproduced well so they belonged to the same species of yellow rumped warbler.

"d.) carbon dioxide and hydrogen sulfide"