QUESTION TEXT: All oceangoing ships carry seawater ballast tanks…
QUESTION TYPE: Necessary Assumption
CONCLUSION: We could stop ballast environmental damage by emptying and refilling ballast tanks in midocean.
REASONING: Oceangoing ships’ ballast tanks need to be emptied. This can cause environmental damage, because ships’ ballast tanks can transport sea creatures from one environment to another. In a new environment, sea creatures can cause environmental harm.
However, sea creatures from the coast usually can’t survive in midocean environments, and vice-versa.
ANALYSIS: There’s no way around it; this is a long question. But don’t panic. When you see a long question, it’s more time effective to slow down and understand it. If you know all the facts in the reasoning above, this question is easy. It’s entering the answers with poor understanding that causes slowness and errors.
The conclusion is that the midocean method is viable. That means it actually has to work, but the stimulus didn’t give us any information on that point. So a necessary assumption is that ships can actually use this method.
(There is a difference between a plan, and a plan that works. For instance, in theory we could get resources from the moon. In practice, we don’t yet have the technology that would make those trips economically viable. The midocean ballast plan is just a plan. Whereas the conclusion is that it’s a viable plan, and the author has given no evidence on whether the plan could actually work.)
- This is a very tempting answer. But it’s a trap. Midocean creatures may be very capable of disturbing other midocean habitats. However, that’s irrelevant, because the stimulus says that the midocean creatures can’t survive in the coastal environments where they will be dumped.
- This makes the argument harder to prove. It certainly isn’t necessary.
- We already know that oceangoing ships can cause environmental harm by transferring sea creatures. Whether or not sea creatures can cause harm by other methods is irrelevant.
- This isn’t necessary. There could be other times that ships pump ballasts, as long as ships aren’t forced to transfer ballast from one coastal environment to another. (or one midocean environment to another)
- CORRECT. If this isn’t true, then the plan is impossible.
Negation: No oceangoing ships are able to maintain stability while pumping ballast in midocean.
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