Do you have the sentence where the author uses the word?
        
             
        
        
        
Groundwater is defined as water that is found beneath the surface of the earth in conditions of 100 percent saturation (if is less than 100 percent saturation,then the water is considered soil moisture).Ninety-eight percent of earth’s available fresh water is groundwater
        
                    
             
        
        
        
<span>Noctilucent clouds (sometimes known as night clouds or mesopheric clouds) form in the mesosphere, a layer of the atmosphere located 47-59 miles above the Earth. </span>
        
             
        
        
        
The right answer would be "C".