Never before had taxpayers confronted so many changes at once as they

Hi Tom,

Let’s first understand how can we use the idiom “so…that…”. Let’s take an example here:

He ate so much that he could not move from his place.

This sentence has two clauses:
i. Tom ate so much (Independent Clause)
ii. that he could not move from his place. (Dependent Clause)

Notice that the IC with “so” is presenting the cause and the DC with “that” is presenting the effect. Why could Tom not move from his place? Tom could not move because he ate a lot of food. So there is a cause-effect relationship between the two clauses. This cause and effect relationship has been established by the idiom “so… that…”. Hence, usage of this idiom establishes the cause-effect relationship.

Now let’s see whether this usage stands true for this idiom in the OG sentence with choice E:

Never before had taxpayers confronted so many changes at once that confronted them the Tax Reform Act of 1986.

If we analyze this sentence, there is no cause and effect relationship between the two clauses. Notice that in sentence “that” is functioning as a relative pronoun that is modifying a slightly far away noun “changes”. However, in the example sentence, “that” is functioning as a conjunction that connects the cause clause with the effect clause. Hence, the usage of “so… that…” is not correct in choice E.

Hope this helps.
Thanks.
Shraddha