During its caterpillar stage, the leopard magpie moth feeds on a plant called the Natal grass cycad and by so doing l...

Grace on December 12, 2018

Using the strategy we were taught,

AKA for a sufficient necessary question, if you negate the answer choices, the correct answer would make the argument fall apart. Negating B makes it fall apart (if they do have the ability and speed, they wouldn't be endangered just because of the other species being endangered as no need for macrozamin). What am I missing?

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Ravi on December 12, 2018

Hi @Glee, the issue with answer choice B is that the negation of this answer choice does not make the argument fall apart. Negating B means that the leopard magpie moth would have the ability to escape from at least one of its potential predators. But what if the leopard magpie moth had 10,000 predators? Its ability to escape from one predator does not necessarily mean it'll avoid extinction. It appears what happened is that in negating B, your translation was not correct. As B is worded before negating, it means that the moth can't escape a single one of its predators. The negation of this does not mean that it can escape all of them; it means that it can escape at least one predator.

Answer choice A, on the other hand, is required by the argument. In negating A, it would mean that feeding on the Natal grass cycad would not be the only means by which the leopard magpie moth could make itself highly unpalatable to predators. In other words, it has multiple ways to make itself unpalatable. If this were true, then the argument would be wrecked, as it would no longer necessarily be true that the leopard magpie moth would also be in danger of extinction.

Grace on December 14, 2018

Thank you Ravi!

Ravi on December 14, 2018

Happy to help, @GLEE!