How do archeologists know that the Harappan civilization in the Indus River valley was advanced? A
It was able to survive monsoon winds which destroyed crops by relying on trade rather than agriculture.
B
It was built next to a cemetery called the hill of the dead and had elaborate military defense systems.
C
It had architecture built with bricks, sanitation systems, and roads arranged in grid-systems.
D
It had a monotheistic religion, a monarchy, and a system of writing using letters.