We can obtain this answer using the process of elimination.
It wouldn't make sense if the cousin was pretending to be stuck inside of a box for a dance, so Option A can't be the correct answer.
It wouldn't make sense if the cousin was pretending to be stuck inside of a box for a choreography, so Option B can't be the correct answer.
It wouldn't make sense if the cousin was pretending to be stuck inside of a box for a speech, so Option D can't be the correct answer.
Therefore, Option C must be the correct answer. As well as this, pantomines can be comedic so it would make most sense for the cousin to be or pretending to be stuck inside of a box in a pantomine.
