Use reasoning to lead to the answer of the following question:
John and Grace live where there are many people, but it's hard for them to move around because of all the what?\nOptions:\n- race track\n- populated areas\n- opera\n- commotion\n- roadblock
 Reasoning process:
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Roadblocks are barricades kept in the middle of the road to stop or deviate traffic. Roadblocks make it difficult to drive around easily on the chosen route. Populated areas tend to have more roadblocks. Therefore, the final answer is roadblock.
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