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Demonstration - demonstrate
Activeness - active
Childless - child
Impossible - possible
Seriousness - serious
Movable - move
Differently - different
Unimportant - important
Useless - use
Reread - read
Unable - able
Preferable - prefer
Glassy - glass
Producer - produce
Dearly - dear
Unhappy - happy
Timeless - time
Happening - happen
Unforgettable - forget
Handful - hand
Restful - rest
Listener - listen
Uncomfortable - comfortable