Here’s the argument’s core structured distilled:

P1: Knowing [an action is good] requires knowing [its consequences are good].
P2: It’s impossible to know [consequences are good].*
________
Con: It’s impossible that [any action is good] in fact.

*The argument makes an implicit inference here: we can’t know the future, and consequences are in the future, so it’s impossible to know consequences.

What we have here is an excellent case study in the distinction between knowledge and fact. From the argument’s premises, we could validly infer it’s impossible to know any action is good. But just because we can’t know something doesn’t mean it can’t be true in fact.

In other words, we can anticipate an assumption along these lines:

If we lack [some kind of] knowledge about good actions, then they can’t happen in fact.

If you’ve got a keen eye for this common distinction, you don’t even really need full comprehension of all the stimulus’ claims here. The following was, genuinely, my experience of this question:

1. Yikes look at all these complex knowledge claims.
2. Oh look, a fact conclusion.
3. Lemme check the answer choices for an assumption that says “fact stuff requires knowledge stuff.”
4. Oh hell yeah! I found one! Now I don’t have to waste time trying to comprehend all those thorny conditionals.

It’s a lot harder to fully understand the stimulus’ structure and dutifully eliminate all the wrong answers than it is to 1) catch facts v. knowledge, and then 2) recognize it in (E). If you missed this question, that should be your main takeaway.