please help!

 

A quiz has four multiple-choice questions; each question is either true or false. How many different solution keys are possible?     

 

Each question has two possible answers, True or False     

 

Q1 has 2 possible answers – so, if there's only one question, there are 2 possible solution keys     

Q2 has 2 possible answers – so, with the previous question, there are 4 possible solution keys     

Q3 has 2 possible answers – with the previous 2 questions, that makes 8 possible solution keys     

Q4 has 2 possible answers – with the other 3 questions, there can be a possible 16 solution keys     

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