Answer: The logarithm of the amplitude of waves recorded by seismographs. 
Explanation:
(Sorry if it’s wrong! I don’t remember it super well, but I think this is it. Also, here’s a picture.)
 
        
                    
             
        
        
        
In urban areas, there are more people, therefore not a lot of farmland. (that eliminates C) If city buildings don't allow flood waters to recede, that could be dangerous in many ways. (So A is still a reasonable answer) If most cities are built in flood zones, there should be some form of shelter if houses aren't safe. Pollutants and diseases being carried in water are already dangerous, but easier to spread with rapid flood waters that are sweeping everywhere. So your best answer would be either A or B.
        
             
        
        
        
6x+4y=13
-(3x+4y=8.5)
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 3x=4.5    =x=4.5/3=1.5
It will be 1.5
        
             
        
        
        
The answer to the question is supposed to be based on 
the information in the graph.  We can't base anything on 
the information in the graph until we see the graph.
        
                    
             
        
        
        
Israel's use of scientific methods to increase the productivity of it's land allows the country to Grow almost all of it's own food.