PrepTest 102

Incorrect. We don't learn about the northern half of the region during the M Era, so it could have been above water, allowing dinosaurs to live there. This could be true, so we can rule it out.

Incorrect. Plesiosaurs lived during the C Period and were aquatic, but that doesn't mean that they lived everywhere there was water. It's possible they were located in another region, not the southern half of this region (even if they could have), and so this answer could be true.

Incorrect. Plesiosaurs lived "exclusively" during the C Period, so they didn't inhabit any region before then. This answer is proven by the stimulus, so it's incorrect.

Incorrect. Similar to (B), dinosaurs could have inhabited that region, but there's no indication that they did. It could have been below water, just like the southern region; or it could have been dry land but with no dinosaurs in sight.

Correct. Argument or Facts:
Facts

Question Type:
Cannot Be True

Stimulus Summary:
C Period (last 75m of M Era) - Entire southern region underwater
M Era - Dinosaurs!
Dinosaur → Lived on land
Plesiosaurs - Lived in water during C Period (not dinosaurs)
Dino species → not Live throughout whole M Era

Answer Anticipation:
Phew, what a stimulus! Before we get to that, however, we should start with the question type.

There, it's asking for what could be true EXCEPT—in other words, four answers could be true, and one can't be true, so this is a Cannot Be True question. That means we're looking for an answer that contradicts the information in the stimulus. Answers that aren't supported or are out of scope could be true and are thus wrong here.

One type of statement that frequently leads to a contradiction is a conditional statement. Since a sufficient condition guarantees the necessary condition, an answer that establishes a sufficient condition but says the necessary is missing cannot be true. Here, we get quite a few conditional statements! Go through our Summary to ensure that you see how to diagram them, but if you just viewed them as strong statements and didn't diagram them out, that's fine, too.

We also get some timeline elements that we should be sure to map out. And one part of the timeline might be particularly important to note—that the C Period is a part of the M Era. We can definitely see them writing some confusing answers on that topic.

Answer Explanation:
The C Period was during the M Era. During the C Period, the southern half of this region was underwater, and dinosaurs lived "only" on land. As such, during this portion of the M Era, dinosaurs couldn't have lived in the southern half of this region. This answer is contradicted by the information in the stimulus, so it cannot be true and is correct.

Key Takeaway:
Cannot Be True questions are looking for answers that are directly contradicted by the information in the stimulus. Answers that are out of scope are, by definition, not contradicted, and so you can eliminate them.