Réponse :
1) A decision must be taken (by you)
2) It will be cleaned up (by them)
3) The customer's name is looked up (by them)
4) He ought to has been told (by someone) that the meeting was at 10 PM.
5) The swimming-pool will be cleaned this weekend (by us)
Explications :
Je t'avoue que je suis pas sûre à 100% pour la 4