What productive resource is scarce for both schools? how does this convince them to trade/exchange with each other?

the answer should be:

their party has more members.

if i am right, give me a 5 star rating!

answer; (d) i believe that the correct answer is americans finally ran out of ammunition;

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.

honestly i love the walking dead, mainly the quotes. “well, pardon me young man, excuse the [insert bad word here] out of my gosh darn french, but did you just threaten me? ” sksk (of course it's not the exact words)