Possessive  s`  `s 

 Slides explanation 

http://englishelxnb1.wordpress.com/2012/11/05/possession-2-possessive-s/
http://www.englisch-hilfen.de/en/exercises/nouns_articles/apostrophe_s.htm

http://elt.oup.com/student/project3rdedition/level1/unit2/grammar/exercise5;jsessionid=61D538D7CBDB949D6DF1DF2CEA6A4A15?cc=co&selLanguage=en

http://www.englishexercises.org/makeagame/viewgame.asp?id=1821

 http://www.englishpower.eu/en/ep-free-lessons/elementary/the-basics/possesive-s/exercise/9-exercise-1-possessive-s

http://www.englishpower.eu/en/ep-free-lessons/elementary/the-basics/possesive-s/exercise/10-exercise-2-possessive-s-or-is?

 http://www.tolearnenglish.com/exercises/exercise-english-1/exercise-english-135.php