I want to say the answer is Tribalism.
Please know i am not CERTAIN this is the answer, but it is similar to a question i had. (Tribalism was the answer)
Probably manufacturing. Farming used to be very prominent but then we switched to technology and lost our use for it as much.
I believe the answer is A, but Im not 100% I hope this helps!
I believe the final answer is correct. Water is a desert's scarcest recourse. <span />