When do you think someone is old enough to be held responsible for there online behavior?
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Explanation:

To the legal system, the answer is clear: children have the requisite moral sense--the ability to tell right from wrong--by age 7 to 15, depending on which state they live in, and so can be held responsible for their actions.

in our power to make a world happy - to teach mankind the art of being so - to a character hitherto unknown - and to have, as it were, a new creation intrusted to our hands, are honors that command reflection, and can neither be too highly estimated,

last one is the answer