Final answer:
The 1993 upper Mississippi River flood was caused primarily by heavy rainfall and rapid snowmelt which led to the overwhelming of the river systems.
Step-by-step explanation:
The two conditions that resulted in the 1993 upper Mississippi River flood were A) Heavy rainfall and B) Rapid snowmelt. The two conditions that resulted in the 1993 upper Mississippi River flood were heavy rainfall and rapid snowmelt. Both of these factors contributed to an excessive amount of water flowing into the river system.
These factors combined over some time to overwhelm the river's system, leading to one of the most devastating floods in recent US history. The heavy rainfall saturated the ground and filled rivers, while the rapid snowmelt added an overwhelming volume of water that the already engorged rivers and tributaries could not accommodate, contributing to severe and widespread flooding.