The answer is A Recognition of value 
        
                    
             
        
        
        
Decaying uranium atoms in the earth's crust result in Radon gas. Radon gas cannot be synthetically or commercially produced.  It is produced as the result of the natural breakdown of uranium i.e. decaying uranium atoms. Radon gas is a naturally occurring radioactive gas. People are exposed to Radon gas via the inhalation and ingestion of the gas. Because it is found in the ground, water or building materials, Radon gas can enter work buildings as well as private dwellings. 
        
             
        
        
        
Answer:
Deposition
Explanation:
Landslides occur under the effect of gravity. When a mass of rock or earth slides down from a mountain or from a cliff then this phenomenon is termed as Landslide. 
Landslides are considered to be a rapid method of erosion.  Wind, waves, running water, glaciers and gravity are the five agents of erosion out of which the gravity influences the process of Landslides. 
Landslides occur suddenly and are dangerous example of the movement of earth materials under the influence of gravity. When weathered material falls away from a cliff, it slides down under the effect of gravity and finally after reaching the hill, the material gets deposited there. This is called Deposition by landslides.