LR Drill Set 14, Question 8
Concerns for the environment have led chemists to(55 more words not shown)
If all of the statements(14 more words not shown)
- ASome materials that(10 more words not shown)
- BSome degradable plastics(10 more words not shown)
- CSome materials that(13 more words not shown)
- DSome materials that(9 more words not shown)
- ESome materials that(14 more words not shown)
Reading the argument
Degradable sounds promising, but breaking down doesn't automatically make a material harmless.
I would want to know what it breaks down into and under what conditions. A material that only breaks down under conditions it never encounters might not solve the problem we hoped it would. The passage gives examples of the needed conditions—sunlight, soil, or water—and then raises a separate concern: some of these plastics leave residues whose toxicity is unknown. Unknown doesn't mean poisonous, but it doesn't establish safety either.
There isn't an argument here for us to prove or attack. We have a set of facts, and the question asks what must follow from them. My initial thought about environmental problems is a reaction, not a conclusion the facts necessarily prove. For example, I can't say the residues are harmful when their toxicity is unknown.
What we’re looking for
Let's keep the given groups straight. All the degradable plastics described are potentially useful packaging materials. Within the degradable-plastics group, we also have different breakdown conditions and some materials that leave those uncertain residues. A correct answer must stay within what those facts establish.
Working the answers
- ACorrect
Take one of the degradable plastics that leaves a residue of unknown toxicity. It is also potentially useful for packaging, because the passage gives that property to all the degradable plastics. So at least some potentially useful packaging materials leave residues of unknown toxicity. We are following the same material through two descriptions, not guessing that separate groups happen to overlap.
- B
We know some require sunlight and some require submersion. They could be different plastics. Nothing says that even one needs both. An example needing sunlight and a different example needing water would satisfy the passage without satisfying B.
- C
The plastics mentioned as needing sunlight are potentially useful for packaging, just like the other degradable plastics. Perhaps some other sunlight-degradable material isn't useful for packaging, but the passage doesn't establish that such a material exists. C adds an example outside what we've been told.
- D
All the residue-producing examples we're given are degradable plastics. Other materials might leave residues of unknown toxicity too, but we haven't been given any. We can't establish that something outside the degradable-plastics group has this property just because some members inside it do.
- E
The soil group and the unknown-toxicity-residue group need not overlap. For example, the soil-dependent plastics could leave residues of known safety, while the uncertain residues could come entirely from water-dependent plastics. The passage would still be true.
Compare this with A: every degradable plastic belongs to the potentially useful packaging group, so the residue-producing plastics must belong there too. No comparable rule puts the residue-producing plastics into the soil-dependent group. That's why A follows and E doesn't.
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