PrepTest 110, Section 3, Question 22
Viruses can have beneficial effects.(59 more words not shown)
If the statements above are(12 more words not shown)
- ARandom mutation makes(6 more words not shown)
- BSome organisms of(17 more words not shown)
- CSome microorganisms that(9 more words not shown)
- DSome viruses that(15 more words not shown)
- ENo virus that(13 more words not shown)
Reading the argument
A virus could help us by killing something harmful. That makes sense. The later claim about how easily it could become dangerous deserves a closer look, though.
Being able to change a virus isn't necessarily the same as being likely to make the particular changes that would make it dangerous. Imagine that a harmful result requires changes to five specific atoms. The fact that random mutations can make much larger changes wouldn't, by itself, show that those five changes happen easily.
But the question gives us a different job. It asks us to take the passage's statements as true and find the one answer that could not also be true. So we aren't choosing a criticism of the argument. We're checking for a direct conflict with what we've been told.
What we’re looking for
Four choices can fit alongside the passage, even if the passage doesn't prove them. The exception must contradict something the passage establishes. I'll keep the distinction clear: “We weren't told that” is not enough to reject a possibility.
Working the answers
- A
This could happen. The passage describes beneficial viruses becoming deadly, but it doesn't say that change can happen in only one direction. Some deadly viruses might become beneficial after a mutation. We don't have to prove that they do; nothing here rules it out.
- B
The passage says complex alterations commonly result from random mutations. It doesn't compare how likely viruses and more complex organisms are to undergo significant alterations. Some more complex organisms could be no more likely to do so. B adds a comparison without contradicting the information given.
- C
Some complex microorganisms could be beneficial while others are deadly. The passage describes some of the harmful ones; it doesn't say that every microorganism more complex than a virus is harmful. C can therefore be true alongside the example.
- D
A virus could fail to kill other viruses and still help humans by killing a harmful, more complex microorganism. The beneficial example in the passage doesn't require a virus to kill another virus. D leaves that example available, so it creates no conflict.
- ECorrect
The passage begins with beneficial viruses and explains that some help by killing more complex microorganisms that are deadly to humans. E says no virus that kills a more complex organism is beneficial to humans. That rules out the very kind of beneficial virus the passage describes.
This is stronger than an unsupported statement: it conflicts with the example we have been told to accept. That is why E is the exception.
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