Answer:
Many scholars believe that the collapse of the Indus Valley Civilization was caused by climate change. ... By 1800 BCE, the Indus Valley climate grew cooler and drier, and a tectonic event may have diverted or disrupted river systems, which were the lifelines of the Indus Valley Civilization.
I think the answer is :
C. Workingmen's party; Chinese exclusion Act
Back then, many immigrants from the mainland of China entered united states and took the majority of middle-lower wages job, leaving little opportunity for the local citizen
hope this helps
True. Is the correct answer. I am sure of it.