Q10 - Large deposits of the rare mineral nahcolite

by **ohthatpatrick** Fri Dec 31, 1999 8:00 pm

Question Type:
Inference (most supported)

Stimulus Breakdown:
CONDITIONAL: If Nah forms, then the atmosphere has at least 1,125 ppm of CO2.
FACT: Nah formed in salty lakes 50-52 million years ago during Eocene epoch.

Answer Anticipation:
We can apply the conditional to the fact that was presented to derive "50-52 million years ago, during the Eocene epoch, at some point the atmosphere had at least 1,125 ppm of CO2.

Correct Answer:
D

Answer Choice Analysis:
(A) Too specific: "most" of the time since then?

(B) Too strong: levels "fluctuated greatly"?

(C) Unknown comparison: we can't compare the saltiness of lakes at different time periods.

(D) YES! That's what we inferred by applying the rule in the 2nd sentence to the fact in the 1st sentence.

(E) Extreme: "NO" significant deposits "AT ANY TIME".

Takeaway/Pattern: On all Inference questions, we're very dubious of strong/specific language. (A), (B), and (E) had fairly prominent red flags. (D) meanwhile, had very safe language … "during at least some part".

We don't count on being able to predict the correct answer in Inference, but we read with a desire to combine 2 or more of the facts presented in order to derive something else. This one only gave us two facts, and they combined in a clear way.

#officialexplanation