PrepTest 143

Incorrect. This answer is too extreme. While the preyed upon birds generally had smaller spleens, and smaller spleens generally indicate health issues, they're both too weak to support this answer about what predators are "unable" to do.

Incorrect. This answer essentially reverses a most statement. Just because most birds killed by predators have smaller spleens doesn't mean most birds with smaller spleens will be killed by predators.

Incorrect. While the argument strongly suggests the predators are generally getting sick birds, there's no indication that they can tell they're sick—it might just be that they're easier to catch.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Health is positively correlated with spleen size in birds. Birds eaten by predators generally have smaller spleens than those that die by accident.

Answer Anticipation:
When a Must Be True stimulus has statements that overlap, the correct answer almost always combines them to form an inference. Here, the two statements both talk about spleen size. If smaller spleens are a sign of sickness, then those birds the predators got were sicker than the ones that die in an accident. The correct answer should draw this connection.

Answer Explanation:
This answer draws the connection formed by the two premises. If predators generally catch birds with small spleens, and birds with small spleens are generally sick, then it can be inferred that the predators are generally catching sicker birds—and thus those birds are more likely to be captured by predators than healthy ones.

Key Takeaway:
Inferences are generally drawn when two statements can be combined. In order to combine two statements, they generally have to overlap—share some key concept. Look for these overlaps in Must Be True questions to better anticipate answers!

Incorrect. Correlation doesn't establish causation! It's just as likely that things causing illness in birds also shrink spleen size or that bird illnesses generally cause the spleen to shrink as it is that the spleen size itself causes illness.