The Curious Incident of the Dog in the Night-time Questions

Im reading the curious incident of the dog in the nighttime and im supposed to
make up a monologue of either mrs. alexander, rhodri or siobhan.
howvever, i dont know which one would be the best to choose and
how to get started, etc.
please help thanks!!

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After you choose between the above characters, who are they supposed to be having a monologue with?