How will the right answer fit in terms of support and conclusion?

Only the right answer will be support that must be true if the conclusion is true. You could also say only the right answer will be support for the conclusion that doesn’t bring in anything new.

Highlight the main conclusion in the passage, if there is one:

these bovines had been domesticated and the people living in the region were no longer exclusively hunter-gatherers.

[BACKGROUND]. [SUPPORT]. [SUPPORT]. Thus, [CONCLUSION].

Domesticated? Where’d they get that from? I’m sure you recognized that the conclusion brought in this totally new thing, which signals that the author changed the subject. So the right answer has to connect the wording of the support to the bovines being “domesticated”.

Map the wording of the answers to the wording of the passage:

(A) Unless they are domesticated…

You love that this maps to the new wording in the conclusion, and to the support about “natural sources of water available”. The passage implies there was no natural water source, and this says only domesticated cows would likely be found in a place like that. If the conclusion is true, that would be pretty much have to be true too.

(B) Domesticating animals is one of the first practices…

You like that this maps to “domesticated”, but what does the order society does things in matter? Even if the conclusion is correct, they could have adopted plenty of other “practices” first.

(C) …other large mammals would have been able to inhabit…

Cool story, but the passage flatly states that “there were no other large mammals there”. What those mammals “would have been able” to do isn’t relevant to whether the bovines are “domesticated”.

(D) …both through agriculture and through hunting and gathering.

This one doesn’t mention “domesticated”, or use any of the same wording from the support. It should be clear that makes this pretty much irrelevant. The bovines could totally be domesticated while some “culture” out there does agriculture and hunting.

(E) …do not need as much water as…

The passage only talks about “sources of water available”. It never says anything about how much water any animals need, and it definitely doesn’t depend on this specific comparison.

(A) is the correct answer.