(01.05 MC)Which of the following best describes the location of the first river valley civilizations?

a Civilizations developed in locations ideal for trade with natural defenses to prevent attack.
b Civilizations developed in remote areas so that they did not have to spend tax money on defense walls.
c Civilizations developed in areas well suited for agriculture but relied on trade for everything else.
d Civilizations developed in areas ideal for trade but low in natural resources and defenses.