Logical reasoning PrepTest 109 · Section 1 · Question 5

Incorrect. This answer reflects the results of the recent study, so it's a premise of the argument.

Incorrect. The argument never states this, so it's out of scope. The closest it gets is comparing the relative weight and volume of plastics and paper in trash, but that's not saying that the ratio between them is the same.

Incorrect. This answer is a statement of the opposing point, so it's not the main point of the argument, since the author stakes out the opposite opinion.

Incorrect. The argument doesn't make such a value judgment or recommendation—it simply states that the current use has a certain balance to it.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Main Point

Stimulus Summary:
Recent study — Representative trash samples show that plastics make up a smaller proportion by both weight and volume than paper.
Principle — Regardless of material the same weight/volume of trash has the same environmental impact.
(Opposing point — Plastic does more harm to the environment than paper.)
Conclusion — Plastic use does less harm to the environment than paper.

Answer Anticipation:
The argument here starts with a study which is almost certainly going to be the basis by which a conclusion is drawn. It then moves on to a general principle establishing what determines the amount of harm that a given amount of trash will do to the environment. Principles that can be applied to provided premises are almost always themselves premises.

This determination is backed up here by the argument using "therefore" in the final sentence and highlighting an opposing point ("Contrary to popular opinion"). When the author of an argument goes against the common belief that's almost always the main point of the argument. When she goes against a common belief and uses a conclusion indicator word it's almost never not the main point of the argument. So here the last line is the main point of the argument:
The current use of plastics does less harm to the environment than paper products.

Answer Explanation:
This answer reflects the last line of the statement. The timeline matches up ("at this time" vs. "current use") and the comparison of the harm done by paper and plastics matches what the author concludes.

Key Takeaway:
When an opposing point is presented the author's opinion of it or the author staking out an opposed stance generally will serve as the main point of the argument.