Logical reasoning PrepTest 142 · Section 4 · Question 4

Incorrect. While modern animals with the same neck structure eating the same food might strengthen this argument, it's not necessary for the argument to work. There could be more than one neck structure set up to let the animal eat from the ground.

Incorrect. While this might be another reason to believe the new theory, it's not necessary for it—even if the diplodocus had full range of vision with its head slightly elevated, it could still have kept its head down to eat.

Incorrect. Again, while this answer might strengthen the argument, it's not necessary. The bone structure could keep the head down even if blood supply didn't.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Old theory Ð Diplodocus ate leaves from treetops by lifting its head
New evidence Ð The bone structure would have made it impossible for the diplodocus to lift its head that high
New theory Ð The neck could bend downward, so the diplodocus must have eaten ground or underwater plants.

Answer Anticipation:
Whenever you see strong language in the conclusion, you should always be wary of it. Here, the argument concludes that the diplodocus "must" have eaten ground and underwater plants. That's pretty strong, especially considering that the premise leading to it establishes only that this "could" be the way that the diplodocus ate.

Since the argument is concluding something must be true based only on it being possible, the correct answer should highlight an alternative and, since it's a Strengthen with Necessary Premise question, rule it out—to reach this conclusion, the argument must rule out all alternatives. Any answer that rules out the diplodocus eating other plants through some means other than lifting its head up will be correct.

Answer Explanation:
The argument establishes the diplodocus couldn't lift its neck up, but that's only one way to get to the high leaves. If it had another method, it might still eat them despite not being able to elevate its head, which would kill the argument.

Key Takeaway:
Strong language in the conclusion isn't supported by weaker premises. When there's a mismatch between a possible explanation and a definite one, alternative explanations should be considered.

Incorrect. If anything, this answer undermines the conclusion by eliminating ways for the diplodocus to find food in one area the argument states they ate.