Experts believe the Indus Valley Civilization began to decline when the Saraswati River started to dry up, or because of a great flood in the area. Why would either event have had a catastrophic impact on the people living there?
A)
Either event would have scared the people into moving away and joining
other civilizations.
B)
Either event would have killed all of the people living there immediately,
thus wiping out the entire civilization.
C)
Either event would have caused protections around the towns and cities to
collapse, leaving the civilization weak to invaders.
D)
Either event would have negatively affected the agriculture (crops and
Livestock), causing their economy to become unsustainable.

PLEASE HELP ASAP