What is the question you are asking
The answer is D. Ignore threats from the cyberbully.
The best way to deal with cyberbullies is to just ignore them, do not respond to them as this is what they want, the attention, the glory. You should always tell an adult you trust for example your parents about any cyberbullying, you should not keep it to yourself as this can be dangerous. It would be sensible to save all the evidence but as far as this question goes the best answer is D.
