解析XML的Android错误：格式不正确

I have an error: Error parsing XML:not well-formed(invaled token) in my activity_main.xml file and I can't figure out for the life of me what it is. I have tried retyping it to ensure it's nothing to do with the quotation marks. I'm pretty much copying across code from a book. The code is:I have an error: Error parsing XML:not well-for