well, never minded,I found out the way. There are no choices and each keyword should lead to a different landing or the same one using different var in the query string. Edit Keyword Settings in Adwords for each keyword. Pretty boring job when you ve got thousands keywords!
What was your solution? Just in case someone else stumbles upon this thread wondering the same thing..
Well I did not figure out a direct way. I just put a different value to my query vars for each keyword using the 'Keyword Settings' option of adwords. ex: myurl/mypage?keyword=key1 myurl/mypage?keyword=key2 ...