Also, for D it doesn't say anything about these two populations being very similar - which paragraph1 says. but I guess D is enough b/c it says interbreed - and as long as you interbreed you can't be the same species ?
thanks! I was confused b/c C says visually indistinguishable which seems to match "very similar" in paragraph 1 since it doesn't specify similar in what way. C also says MUTUALLY isolated which I thought was the same as reproductive isolation? thoug…