Can | Do | Does | Is |
Are |
Was | Were |
Could |
Should |
Would |
Won't |
Will |
Which |
May |
http://www.english-zone.com/grammar/questions2.htm
http://a4esl.org/q/f/z/zz87mca.htm
http://a4esl.org/q/j/ck/fb-queswords.html
http://www.1-language.com/englishcourse/unit7_index.htm