The small experimental thing doesn’t make sense to me. A seems airtight. By stating that vacuum tubes don't meet the carrying capacity needed to be equivalent to semiconductors, the passage essentially makes the heat tolerance requirement irrelevant - because, even if the larger group of vacuum tubes were heat tolerant, as the small experimental subgroup is stated to be, they wouldn’t meet the other condition needed (carrying capacity). So, we can say that it must be true that they are not an acceptable replacement.

I got it right but I disregarded the answers involving the car analogy as I identified that as context and thus irrelevant to the argument's structure. Did anyone else think this way?