can and can't in sentences and questions

http://www.englishexercises.org/makeagame/viewgame.asp?id=1518
http://www.englishexercises.org/makeagame/viewgame.asp?id=5204
http://www.englisch-hilfen.de/en/exercises/questions/can2.htm
http://www.englishgrammarsecrets.com/can/exercise1.html
http://www.englishgrammarsecrets.com/can/exercise3.html
http://www.englishgrammarsecrets.com/can/exercise4.html