The best answer is C: II and III.
To protect her gains, Mary should consider strategies that limit her potential losses. Of the choices listed, the best strategies to protect Mary's gains would be to close out her short position (III) or buy puts on XYZ (II).
Buying calls on XYZ (I) would not protect Mary's gains, as it would only allow her to potentially make more money if the price of XYZ goes up. Buying more XYZ using leverage (IV) would also not protect Mary's gains, as it would expose her to even more risk if the price of XYZ goes down.
Therefore, The best answer is C: II and III.
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