The vital point is that each branch of the argument is treated in a paragraph of its own. The essay steps the reader through the argument one branch at a time, working from the top of the branch to the bottom, before signaling the shift to examining another branch.
Here's the model answer:
© Austhink 2007. Rationale Exercises version 0.1, Sep-07
Note: these exercises are undergoing continual improvement. Next time you come back they might be a bit different.
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