The hedgehog will give you four options. Simply type the number 1, 2, 3, or 4 to answer. The project will continue until you stop it. Also, some of the root words have very similar meanings and it will still count you as wrong if you choose a similar meaning. I'm not going to fix that, because it would be a waste of time for such a small issue - sorry.
I am learning root words from the Merriam-Webster's Vocabulary Builder. It is a book with many roots and example words.
