What if I do not know the answer to their question?

           If you do not know not the answer to a question that they ask, then that is a good thing! So don't worry about it.  Turn it into an opportunity to talk to them more later and get some vital follow-up information, which is what you want anyway!    

So you can say something like: "You know, that is a good question.  I'll ask my pastor or an elder in my church and find out the answer.   If you give me your phone number or e-mail address, then I call call you with the answer to that question.  I'm glad you are interested to know the truth about the Gospel and where you will spend eternity.  Any questions that I can answer to help you come to a decision, I would be glad to make the effort to find out for you..."

     The Bible says in 1 Peter 3:15:  “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."

And yet if you do not know, then try to get their phone number or e-mail address, so that you can answer their question later and follow up to give them more info and also so that you can invite them to your church.