I think you wanted to know whether the statement in question is true or false. Based on this assumption, i am answering this question and hope that it helps you. It is absolutely true that the slash and burn system of deforestation reduces the number of oxygen producing and puts more carbon in the air.
        
                    
             
        
        
        
According to the 2011 Earth Science Reference Table, Selenite Gypsum has an approximate hardness of 2. 
The hardness of calcite is 3. 
The hardness of apatite is 5 according to the Moh's hardness scale. 
The hardness of diamond is 10.
        
                    
             
        
        
        
Answer:
If the hydronium concentration increases, the pH decreases, causing the solution to become more acidic. This happens when an acid is introduced. As H+ ions dissociate from the acid and bond with water, they form hydronium ions, thus increasing the hydronium concentration of the solution.