My answer choice is E but the right answer is A.
I can understand why A is right, but I think E also makes sense.
I guess the primary purpose must show the key words
The problem with (E) is that the it actually contradicts the passage. The passage doesn't say that large manufacturing plants usually don't help manufacturers achieve economies of scale. It says that having a large plant (= tangible capital) alone is not enough to achieve realized economies of scale. Rather, you need tangible capital + intangible capital. But tangible capital does help, so (E) is incorrect. The text explanation in the OG says this as well.
1 Explanation