There is supposed to be an error on the "How ignorant are our teenager's?" quiz. Anyone figured it out?

On February 29, Common Core, an educational advocacy group, issued results of a test of general history and literature that it administered to 1200 high school students. The results were dismal with less than half knowing when the Civil War was fought and only 61% knowing what the Renaissance was.
However, in the New York Times last week, Dick Cavett posited the ironic comment that one of the “correct” mulitple choice answers shown on the Common Core website was itself WRONG. Anyone figured out which one it is? I have one likely candidate but I won’t mention it here and will post it in an answer.
The quiz is here http://commoncore.org/_docs/CCreport_stillatrisk_quiz.pdf and Cavett’s blog is here: http://cavett.blogs.nytimes.com/2008/03/14/uncommoner-than-thou-buckley-part-two/index.html?ref=opinion