Confused about what global variables are. At my exam we were not allowed to use global variables. I was confused exactly what a global variable was and accidentally used global variables in my program. I failed the exam and next week I have the exam again but I'm stilll confused. Please tell me which of the following situations have a global variable. I will just use 'a' to refer to this potential global variable, and the code will be pseudo.  

  
    a = 0  
    def function():
      #change a in some way  


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    def function(x):
     #do something to x
    def main():   
     a = 0   
     function(a)    
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    def function(x):   
     #do something to x  
    a = function(a)  
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    a = int(input(""))   
    def function(x):  
     # do something to x while using a