Carbon (C) is an element
Carbon Dioxide (CO2) is a compound
Hydrogen (H) is an element
Sodium Chloride (NaCl) is a compound
A good way to tell whether something is a compound or an element, is that in a compound there is a mixture of different elements. Like in Carbon Dioxide, the symbol is CO2. This shows the carbon (C) and oxygen (O) together. I hope i worded that well enough and this helps :) 
        
                    
             
        
        
        
One way is that Igneous rock could erode and become sediment and deposited and slowly change into sedimentary rock, then get pushed down deep into the crust and changed by heat and pressure into metamorphic rock.
        
             
        
        
        
Answer:
A. There are more people on transplantation lists than donor organs so xenotransplantation can save people’s lives
Explanation:
Xenotransplantation, ie using non human animal organs in transplantation, has following most crucial favouring argument 
- Patients needing transplanted organs are much higher than people willing & able to donate them. So, there is extreme excess demand, needed to be satisfied for saving people's lives.
 
        
                    
             
        
        
        
What are the test options?
        
                    
             
        
        
        
To tell you the truth, all rocks can melt under heat and pressure. For example, if a volcano erupts, the magma that is flowing can melt the rocks because of extreme heat.