PrepTest 133, Section 1, Question 6
Small experimental vacuum tubes can operate in heat(59 more words not shown)
If the statements above are(10 more words not shown)
- AVacuum tubes are(10 more words not shown)
- BOnce vacuum tubes(16 more words not shown)
- CThe only reason(20 more words not shown)
- DSemiconductors will always(14 more words not shown)
- EResistance to heat(10 more words not shown)
Reading the argument
The vacuum tubes handle heat better. That sounds promising—until we read the condition attached to using that advantage.
Better heat resistance is not enough. To be preferable for digital circuits, a component also has to be comparable to semiconductors in every other significant respect. Maximum current capacity is one of those respects, and vacuum tubes presently fail that comparison. One unmet requirement is enough to stop us from calling them preferable.
What we’re looking for
For the must-be-true question, I'd keep the conclusion modest: vacuum tubes aren't preferable for this use right now. Don't turn that into a claim that they can never improve, or that current capacity is their only problem. We've been shown one obstacle. There could be others.
Working the answers
- ACorrect
Vacuum tubes don't currently meet the stated requirement concerning maximum current capacity. Since being comparable in that respect is required before they can be preferable, their heat advantage doesn't get them over the line. This is a conclusion about preference for digital circuits now, exactly the use and time the passage discusses.
- B
Fixing current capacity might remove one obstacle while leaving another. Perhaps cost or durability is also a significant respect in which the tubes aren't comparable. The passage says all significant respects must be comparable, and current capacity is just the example we're given.
B also predicts actual use. Even being preferable wouldn't by itself tell us that somebody will put the tubes into a circuit. The facts don't guarantee the outcome B describes.
- C
We don't know this is the only obstacle, and we aren't even told that the current capacity is too low. The passage says it isn't comparable; C supplies a direction for that difference. It also assumes the tubes aren't being used, whereas the passage concerns whether they are preferable. Those are stronger claims than the facts give us.
- D
Always is a prediction about the future. Maybe engineers will improve the vacuum tubes. And what do we know about applications other than digital circuits? Nothing here establishes which component is better for those uses. D moves beyond both the time and the application discussed.
- E
Heat resistance is one known advantage, not necessarily the only advantage. Vacuum tubes could have another benefit we haven't been told about and still fail the current-capacity requirement. Knowing one benefit and one unmet requirement doesn't give us a complete list of every difference between the two technologies.
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