Réponse : sing+er

arrive+ al=arrival

exist+ence=existence

employ+ee=employee

real+ize=realize

strength+en=strengthen

easy+ly=easily

probable+ly=probably

wash+able=washable

amuse+ing=amusing

scare+Y=scary

hope+ful=hopeful

care+less=careless

child+ish=childish

friend+ly=friendly