Is it a problem that I don't see what the issue is with answer choice A?

- Small experimental is a type/subset of vacuum tubes > the text says that vacuum tubes max current capacity are not comparable to semis > therefore small experimental max current cap is not comparable to semis

Answer A has to be correct. We know "vacuum tubes" are lacking a comparable significant respect (max current capacity), which makes them not preferable. Also, answer A doesn't mention "small experimental", so even if you think that "vacuum tubes" doesn't mean all vacuum tubes and does not specify for "small experimental" subset, it's irrelevant to answer choice A.

I still don't see how idea C is only a possible outcome of B ("B could cause C"). There is no definite language to say it is only a possibility.

Moreover, the question stem says, "The economist's statements, if true..." and the curriculum has taught to use only what is in the stimulus text and question stem.

Despite that I agree, applying the B > C relationship in the real world would only be a possibility, this would be thinking outside of the parameters of the question, so inferring "could" seems wrong for testing/question answering purposes

Wow this lesson turned personal into life advice haha. I totally agree with the ideas of honesty and of pre-confusion but have always wondered, what is a good way to check/identify if you are pre-confused? Frequent periodic testing of comprehension?