Answer:
A secret. When you have a secret, you want to tell other people, but when you do, it's no longer a secret.
 
        
                    
             
        
        
        
Answer:
1. Obtain two identical containers and dry sand.
2. Shape equal amounts of sand into a  "slope on the side of"  each container.
3. Spray water on the sand in one container. The sprayed water represents "rainfall"
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4. In the other container,  "place ice cubes to melt on the sand. This represents snow or glaciers."
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5. Observe and record the changes in the sand.
6. Analyze differences between the two containers.
Explanation:
Mine hasn't been graded yet but I'm pretty sure this is the right answer. I'll come back once it's graded and say.
 
        
             
        
        
        
Ulna is the forearm bone involved in formation of elbow joint