Premise: Seawater vapor contains more oxygen 16 and less oxygen 18 than the seawater itself.
What does this mean? When evaporation occurs, the ocean loses more molecules of oxygen 16 than of oxygen 18. This would give the ocean itself a higher concentration of O18. However, when the chemicals return via precipitation, the original ratio is restored.
Premise: During an ice age, a large amount of precipitation falls on ice caps where it is trapped as ice.
The molecules drawn from the ocean through precipitation are trapped as ice, and thus not able to return to the ocean. This means that the original ratio is not restored. Therefore, the higher concentration of O18 remains. This is why B is correct.
C is incorrect, because the only information we have about the ice age is that ice caps gather more precipitation. We are not told that the chemical makeup of rain or snow changes during these times. As far as we know, it is still more O16 / less O18 as given to us by the premise.
LSATChrisOctober 10, 2019
Sorry this isn't the question I was referring too
SamAOctober 11, 2019
@LSATChris,
Strange, for some reason it linked me to the wrong question, @ me and let me know the test, section, and question number and hopefully I can help. I was wondering why the answer choices didn't match up.
