GMAT Critical Reasoning (CR) | It is a mistake to give post office employees individual

It is a mistake to give post office employees individual discretion as to when to inspect or open suspicious packages. If individual employees are allowed to open “suspicious” packages without first following a strict protocol, it is only a matter of time before all packages will arrive having already been opened due to some postal employee’s idle curiosity.

The conclusion above is based on which of the following assumptions?
* Postal service managers are the only people with the authority