Who is going to harm you if you are eager to do good? But even if you should suffer for what is right, you are blessed. "Do not fear their threats; do not be frightened." But in your hearts revere Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience, so that those who speak maliciously against your good behavior in Christ may be ashamed of their slander. -- I Peter 3:13-16, NIV (emphasis supplied)
The same kindness and humility that inspired their questions, in other words, must be shown when we answer their questions.
In short, our goal is to show them Christ -- to show Christ in what we say and how we say it.
Even if they don't know anything else.