CAN & CAN'T

http://www.agendaweb.org/verbs/can-exercises.HTML
http://www.englisch-hilfen.de/en/exercises/modals/can2.htm
http://www.saberingles.com.ar/curso/lesson13/05.HTML
http://first-english.org/english_learning/english_beginners/can_can_t_exercises/a_can_can_t_exercises.htm