It has been hypothesized that our solar system was formed from a cloud of gas and dust produced by a supernova—an esp...

Naz on October 1, 2014

Here we have a strengthen with necessary premise question. Remember that a premise is necessary for a conclusion if the falsity of the premise guarantees or brings about the falsity of the conclusion. First we check to see if the answer choice strengthens the passage, and then, if it does strengthen, we negate the answer choice to see if its negation makes the argument fall apart. If the answer choice does both those things then it is our correct answer.

The conclusion of the argument is that the hypothesis is disproved.

Why? The hypothesis is that our solar system was formed from a cloud of gas and dust produced by a supernova. We know that supernovas produce the isotope iron-60, so if the hypothesis were correct, then iron-60 would have been present in the early history of the solar system. However, we know that researchers have not found any iron-60 in meteorites that formed early in the solar system's history.

So, we know that the hypothesis being correct depends on iron-60 being present in the early history of the solar system. The argument then concludes that the hypothesis isn't correct because researchers haven't found any iron-60 in meteorites that formed early in the solar system's history.

The first question that should jump out at you is, why does no evidence of iron-60 in meteorites mean that there was no iron-60 present?

Answer choice (E) states: "If there had been iron-60 present in the early history of the solar system, it would be found in meteorites formed early in the solar system's history."

Does this strengthen the argument? Yes. This gives us a link connecting us from "researchers have found no iron-60 in meteorites" to "the hypothesis is disproved." Answer choice (E) states if there were iron-60 in the early history of the solar system, then it would have been found in meteorites formed early in the solar system's history.

We know that no iron-60 was found, therefore there was no iron-60 present in the early history of the solar system. So, this strengthens the conclusion that the hypothesis is incorrect because the hypothesis being correct requires the presence of iron-60.

Does the negation of the answer choice make the argument fall apart? Yes. Negation: If there had been iron-60 present in the early history of the solar system, it would not necessarily have been found in meteorites that formed early in the solar system's history. This makes the argument fall apart because we can no longer say because no iron-60 has been found in meteorites that formed early in the solar system's history, that no iron-60 was present--since the negation states that iron-60 does not necessarily need to be found in meteorites for it to have been present in the early history of the solar system. So, we cannot conclude that the hypothesis is disproved.

Hope that clears things up! Please let us know if you have any other questions.