how: long, far, often?????

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-10785.php

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-24600.php

http://www.englishexercises.org/makeagame/viewgame.asp?id=8224

http://www.englishexercises.org/makeagame/viewgame.asp?id=1884