I think your reasoning is more black and white than it needs to be. In other words, just because it was "easiest" to domesticate in the past than it is today does not mean that it is necessarily "difficult" to domesticate them today. It could be easy, but the past was just easier. If that's the case, then it goes against the author's conclusion (that it was either too difficult or unworthy). I hope that makes sense lol.

I think this falls under the "the correct answer doesn't have to be perfect" category... which is inherently annoying. But, we need to assume the most logical definition of "congestion", which is that it is packed and slow-moving. Also the fact that all the other answers suck (by POE), D is the only right answer.

At this point, he says he doesn't expect us to complete the questions within the timeframe. We are practicing getting our accuracy down, and will eventually be able to do all these steps quicker. I think you're on the right track if you're getting them right in general! This lesson is still early in the process :)