#23 - Global Reference, Must Be True

[Luke Haqq]

Hi marioncarroll!

This is a must be true question. That means that, if you come across an answer choice that seems "likely true" based on the passage but is not necessarily true based on it, then you can eliminate that as an incorrect answer choice. It's important to remember, though, that things can be necessarily true based on the passage even if they aren't stated explicitly within it. There may be an array of things that are implied by a passage, and this can be fair game for a must be true question type.

Here, answer choice (E) asks, "Which constituent element of CFCs is most damaging to ozone?" This should direct you to the second paragraph, which discusses "constituent elements" (line 26) of CFCs. More specifically, the only constituent element mentioned is chlorine, which we are told is very devastating to the ozone layer. As Jeff mentions above, it would have been "a serious and problematic omission" to focus on the damage of chlorine but not mention a more damaging constituent, so the implication is that chlorine is the most damaging.

[99bengardner@gmail.com]

I'd like to mention that chlorine is discussed only in the context of freon gas (a subtype of CFC).

"Which constituent element of CFCs is most damaging to ozone?" is also an odd question because CFCs do not have constituent elements. CFCs is a grouping of molecular structures, and those structures are what have constituent elements. Analogous "Which mammalian body part has the most digits, hand or feet?" Chlorine is not established as the relevant constituent element for all CFCs but rather only for the studied freon gasses.

The question then requires that we assume "The researchers are studying the subtype of CFC that possesses the most damaging constituent element." For an implication, as opposed to "The experiments involving freon gasses also involved a lab", the former seems to me to be massive.