It is a mistake to give post office employees individual discretion as

Dear Anazeer,

I'm happy to respond.

To be honest, my friend, I don't think this is a superb question. Here's my analysis.
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?
(A) Postal service managers are the only people with the authority to open suspicious packages.
This is out-of-scope. The new plan being discussed he would give everybody the authority, the discretion, to open packages. What's the current plan that would be replaced by this new plan? We don't know. This is irrelevant and wrong.

(B) Suspicious packages are indistinguishable from all other kinds of package.
Suppose (completely unrealistically!) that there were clear markings to distinguish suspicious packages, say, stickers such as "Bomb Contained-Please Ignore Ticking" or "Terrorists-R-Us" or something of that sort. Well, if the post office employees really had individual discretion to open whatever they want, there is nothing preventing them opening the perfectly safe packages just out of curiosity. This would make the new plan an even worse idea than it was before: if anyone could clearly tell the difference between safe vs. unsafe packages, why on earth would it make sense to give people discretion rather than simply tell them only to open the unsafe packages? Negating this actually strengthens the argument, so this is not an assumption.

(C) The efficiency of the postal service will be greatly reduced if more packages are inspected.
Efficiency is out of scope. This is wrong.

(D) There is currently no protocol in place for the inspection of suspicious packages.
It's unclear whether there is a protocol in place or not. Perhaps there is and no one follows it--we don't know. This is wrong.

(E) Postal employees desire to open packages out of curiosity.
It would be extremely hard to explain the conclusion without the curiosity-run-wild of the postal employees. What is unsatisfying about this as an OA is that there was no attempt to paraphrase. Rarely would an official question have an OA with wording so close to the conclusion of the argument: that makes this question too easy.

This is not a terrible question, but it's not the best. It falls well short of the standards of the GMAT CR.

Does all this make sense?
Mike