D: All the variables are controlled except one.
        
                    
             
        
        
        
The answer is actually <u>true</u><u>.</u>
The starting point of all rivers is higher than their end point. However, under the right conditions, small amounts of water can be drawn upwards, against the tug of gravity, through a phenomenon known as "capillary action". For this to occur, however, the water must be confined into a small flow space.
Hope this helps!  If it does, would you mind marking my answer as Brainliest? Thanks :D
        
             
        
        
        
Things too small to be viewed by a light microscope can be viewed with an Electron Microscope
Hope this helps!