Question

How could shifts in the physical environment have caused major changes in early civilizations (select 2)

Answer 1

The correct options are B AND D.
Agriculture was the major means of survival for men during the early days. Fluctuations in the rainfall during the course of a year may adversely affect the crops grown. If this persists for a long time it will leads to food shortage and famine. 
Earthquake and eruption volcanoes are shift in the physical environment which can easily destroy any community.