Why do you think people in early cities began to trade with other cities?

Early cities began to trade with other cities because it allowed them to access materials or supplies that were not common or not accessible in their community.

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.

nations must cooperate to bring about and maintain world peace.

nations must not wage wars or commit war crimes in a desire to control other nations.

i think i know which options you have but if these aren't options let me know