Answer:
Charge the balloon, hold it near an electroscope, and determine if the electroscope leaves move.
Explanation:
The gold leaf electroscope is an instrument used to detect if a body is charged. It has two gold leafs suspended from a brass stem in a vacuumed glass jar and connected to a metal cap(Toppr).
When the test body is allowed to touch the metal cap, a change in the size of the leaves shows whether the body is charged or not.
Since we are suspecting the balloon to be made up of a metal; metals can be charged. We can test if there is really a charge on the balloon by bringing it near an electroscope to see if the electroscope moves.
 
        
             
        
        
        
The answer is C because it is believed that those two were once connected
        
             
        
        
        
Observations, surveys, and models.