- Mon Sep 16, 2019 1:57 pm
In short, C is wrong because, while it's supportable from the passage, it's too narrow to be the main point. Answer choice C is primarily summarizing the second paragraph of the passage, which documents the difference between observed temperatures and what greenhouse theory originally predicted.
One of the things the main point needs to include here is a statement about the author's position on the causal explanation for global warming. The final sentence of the passage nicely sums up the author's position: "changes in the earth's atmosphere have raised its equilibrium temperature, and ... greenhouse gases represent the best explanation of that shift." That "best explanation" position is missing from answer choice C, which merely states that temperature has been "rising in a way that is consistent with the greenhouse theory." Being consistent with a theory is not quite strong enough to capture the causal implication of the last sentence of the passage (that greenhouse gases are causing global warming). Answer choice D better captures that by stating that "the greenhouse effect is a major cause of this warming trend."
I hope this helps!