Only thinkers know what should be on the question mark

 Only smart people can find what should be on the question mark in the image below

Try to give this one to your friend to test there IQ there is no time limit for this one but smart people can solve it within 10 seconds 

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Times up for people who tried with the count down here is the solution if you didn't answer

There should be the letter R because this is the pattern of a shifting gear this on tricked your brain try out more