As any other ancient civilization, the Sumerians were traders as well. And they had a few good reasons to do this. 
Because they traded, their trading partners were less likely to attack them, because it would hurt their economy as well. Furthermore, they didn't produce everything they needed and traded those goods with goods which they produced too much of. 
And lastly, through trade they could also get exotic goods which they would have never gotten otherwise. 
        
             
        
        
        
Answer:
The correct answer would be a. the sum of all genetic traits in a population’s individuals at a given time.
A gene pool is defined as a sum total of all the genes present in an inter-breeding population at a specific time.
It includes all the alleles of all the loci within the genes of a interbreeding population or species.
The composition of the gene pool of a population can change with course of a time due to evolution.
A large and diverse gene pool enhances the ability of a population to adapt, survive and evolve in a nature.
 
        
             
        
        
        
Answer:
Gravity
Explanation:
Percolation is the process of a liquid slowly passing through a filter. It's how coffee is usually made. Percolation comes from the Latin word percolare, which means "to strain through." Percolation happens when liquid is strained through a filter, like when someone makes coffee.
Evaporation-the process of turning from liquid into vapor.
Condensation-water which collects as droplets on a cold surface when humid air is in contact with it. 
and gravity- Gravity is the force of attraction between two objects, and Earth's gravity pulls matter downward, toward its center. It pulls precipitation down from clouds and pulls water downhill. The warm water near the surface of the ocean heats up with sunlight and evaporates, keeping the water cycle in motion.
 
        
             
        
        
        
Tapirs,anacondas,or caimans.<span />