Verb BE "Present"

http://www.learnenglish.be/gr1_tobe_study.htm

http://www.englishmaven.org/HP6/To_Be_Exercise4.htm

http://www.english-room.com/index.php?option=com_wrapper&Itemid=33

http://www.englishbee.net/lessons/basic_exer/tobe/to_be_negative/verb_to_be_negative.htm