PrepTest 118

Incorrect. The analog system here has a theoretical benefit and practical downside, but that doesn't mean that it doesn't work well in practice—it could work well despite that downside, especially if it's not being duplicated. Also, the stimulus features a single example of this proposition, which isn't enough to support the idea that it's true "[m]any" times.

Incorrect. There's no discussion of needs, so we can't say that the infinite detail of an analog system isn't necessary.

Incorrect. First, the stimulus discusses only two systems, so we can't say that digital systems are the "best"—implying that they're better than all other systems. Second while it can be inferred that digital systems copy better than analog ones we can't infer that it's impossible for errors to occur ("cannot occur")—they could occur just very infrequently. Finally the errors crop up in the copying of the signal according to the stimulus not in the emission of the signal which isn't discussed.

Incorrect. The stimulus notes one practical disadvantage of analog signals, but that's not enough to support the idea that they're worse for "most" practical purposes. Most purposes might not involve copying them!

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Theoretical — Analog is better than digital since the former is infinitely detailed and the latter isn't
Practical — Copying an analog signal results in errors that eventually destroy the original signal

Answer Anticipation:
The stimulus here creates, essentially, a pros/cons list for digital vs. analog systems. The latter is better because you can copy it without the signal degrading, which isn't true of the latter. The former is better because the original is infinitely detailed, which isn't true of the latter.

With these comparisons in mind, let's head to the answer choices to find one that is backed up by it. This is very much a Must Be True question where knowing the details and heading to the answers ASAP is going to yield the fastest answer!

Answer Explanation:
The noted downside of analog systems is that copying them degrades the signal. As such, digital systems can be said to be better in situations where the signal needs to be copied many times, as it won't degrade that signal as it will in analog systems. This answer is supported by the comparison in the stimulus, so it's correct.

Key Takeaway:
Comparisons are frequently relevant to the correct answer in Must Be True questions—and that's especially the case when the comparisons amount to a pros/cons list. Also note how the correct answer here brought a goal into it (successfully copying something many times)—goals are another frequently relevant concept on the LSAT.