CHRISTIANS: How would you demonstrate-with reason-that the Bible is the one true word of God?

You must always start by remembering that we are talking about God. He sees what we don't. He is supernatural. We are natural. He also says to "test" Him on what is written in the Word of God. It will take some research on your part but start at the beginning and notice correlations between things that have been proven historically and what is in the Bible. Find a copy of an Archeology Bible. This should be a helpful resource.