EatMyDosa wrote:
Does option E mildly strengthen the conclusion? Kindly help me understand on what basis would you reject option E?
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.
Let's take a look at the passage again before looking at (E).
The conclusion of the passage is: if two stars have the same composition, they must have come from the same gas cloud.
The evidence for this is:
1) Stars are born in groups and each group originates from a single gas cloud
2) Each gas cloud has a unique, homogenous composition
We're asked to find the answer choice that best strengthens this argument. (E) tells us:
Quote:
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.
There's a small gap in the passage's logic: we're not told that the chemical composition of the gas cloud is inherited by the stars it produces. So, even if there is a nice, homogeneous mix of chemicals in the cloud, maybe they get separated or skewed or changed or whatever else when the stars are created.
(E) tells us that astronomers can at least sometimes tell whether a star has the same chemical composition as its parent gas cloud. This doesn't fill in the gap in the passage's logic. The astronomer's ABILITY to determine whether a star has the same chemical composition as its parent gas cloud doesn't tell us whether the star HAS the same chemical composition as its parent gas cloud.
From the information given in (E), we don't know if the results of the test these astronomers perform would support or undermine the claim in the passage. This means (E) cannot strengthen the argument -- (E) is not our answer.
Compare this to (C):
Quote:
(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
This fills in the gap in the passage's logic perfectly. It tells us that whenever a star is formed, it has the same chemical composition as its parent cloud of gas. Since we know each cloud of gas has a
unique, homogenous chemical composition, we can tell which cloud of gas a star has originated from by its chemical composition.
(C) strengthens the argument by filling in the gap in the passage's logic -- (C) is the answer to this question.
I hope that helps!