Hi!
The answer would be A. Police.
The police are the authorities that maintain law and order, and are responsible for ensuring safety of the public. There duty is to enforce the law, and not to give out punishments for those who go on to break it. If individuals out of a population are seen carrying out illegal activities or breaking the law, they are first picked up by the police, and later on trialed by the justice system (where the court and juries are then involved).
Probation is a period of time in which the defender/offender is required to observe particular limitations and rules and is on supervision. This is a sanction that is decreed by the court, and is not the primary connection, but a stage in the criminal justice system.
Hope this helps!