The correct word to complete the sentence is 'estadio,' as it is the venue where soccer is played. Other options do not match the context of playing sports. Therefore, 'Los muchachos juegan al fútbol en el estadio.'
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The correct word to complete the sentence is 'estadio', as it refers to a stadium where soccer is played. The other options do not fit the context of playing soccer. A stadium is the appropriate venue for such activities. ;