I don't get what you are saying... Can you reword it?
 
        
             
        
        
        
The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.
        
                    
             
        
        
        
Answer:
A. The balloons will increase to twice their original volume.
Explanation:
Boyle's law states that the pressure exerted on a gas is inversely proportional to the volume occupied by the gas at constant temperature. That is:
P ∝ 1/V
P = k/V
PV = k (constant)
P = pressure, V = volume.

Let the initial pressure of the balloon be P, i.e.  , initial volume be V, i.e.
, initial volume be V, i.e.  . The pressure is then halved, i.e.
. The pressure is then halved, i.e.  
 

Therefore the balloon volume will increase to twice their original volume.