How can i compare the arrays userResponse and correctAnswers in the gradeAnswers function. It is the only pary not functioning properly

def main():

    correctAnswers = ['B','D','A','A','C',
                      'A','B','A','C','D',
                      'B','C','D','A','D',
                      'C','C','B','D','A']

    userResponse = userAnswers()
    correct = gradeAnswers(correctAnswers, userResponse)
    passFail(correct)


#function to obtain the users input for answers and put in an array
def userAnswers():

    answers = 1

    userResponse = ['','','','','','','','','','',
                    '','','','','','','','','','',]

    for answers in range (20):
            print('What is the answer to number ',\
                answers + 1, '? ',sep='',end='') 
            userResponse[answers] = str(input())


    print(userResponse)
    return userResponse   




#function to calculates the amount of correct answers and displays such
def gradeAnswers(correctAnswers, userResponse):
    correct = 1
    incorrect = 0
    index = 1
    for correct in range (20):

            if userResponse[correct] == correctAnswers[index]:
                index += 1
                correct += 1**




    print('You answered',correct, 'out of 20 questions correctly')

    return correct***


#function to determine and display wether the user passed or failed
def passFail(correct):

    if correct >= 15:
        print('You passed.  Good Job')
    else:
        print('You failed.  Do Better')



main()