Present participle; Past participle - challenging - challenged Present - challenge - challenge - challenges - challenge - challenge - challenge Past - challenged - challenged - challenged - challenged - challenged - challenged Future - will challenge - will challenge - will challenge - will challenge - will challenge - will challenge Present conditional - would challenge - would challenge - would challenge - would challenge - would challenge - would challenge Present Perfect - have challenged - have challenged - has challenged - have challenged - have challenged - have challenged Past Perfect - had challenged - had challenged - had challenged - had challenged - had challenged - had challenged Future Perfect - will have challenged - will have challenged - will have challenged - will have challenged - will have challenged - will have challenged Past conditional - would have challenged - would have challenged - would have challenged - would have challenged - would have challenged - would have challenged Imperative - - - challenge - - - - - - - -