I think the best thing to do is to just be honest when they ask. Because, even if you tell them something else, they are going to find out in school and it will be ten times worse. I understand some things are too mature for an 8 year old, but my parents had always told be the truth when I asked and I grew up just fine. If they told me something I didnt match up with other storys id look it up on the internet or at school and WOW lol like I said they wished they would have just told me the first time around.