#4 - Concept Reference, Must Be True

[Administrator]

Complete Question Explanation

The correct answer choice is (E).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D):

Answer choice (E):

This explanation is still in progress. Please post any questions below!

[goingslow]

Hi! I have a question about answer choice (D), "It can contain a high concentration of salt as a result of contamination by deep-well-injected wastes."

I'm unclear on the keyword "underground water" in the question stem.

Is underground water exclusively drinkable water in aquifers? Or does underground water also include salt water in the porous and permeable rock strata, into which liquid waste is injected?

A related question is about what "underground water" refers to in paragraph 3. “Unlike surface water, the water in underground rock strata does not flow entirely under the influence of gravity.” What does the “water” refer to? Drinking water or liquid wastes? I thought it was drinking water, but in paragraph 4 the passage talks about “uncertainty about where injected wastes will flow.”

Thank you so much!!!

[katehos]

Hi goingslow!

"Underground water" in this question stem and paragraph 3 refers to any of the water that is underground (either salt water or drinking water)! The liquid waste is not water, but rather a toxic byproduct of the 'industries' mentioned in the beginning of the passage. This liquid waste flows similarly to water and can contaminate underground water, but it's different from the water itself!

I think part of your confusion can be addressed by pointing out how liquid waste, even though it is not underground water, can mix with underground water and thus move the same way that the underground water does (discussion of waste mixing with water can be found in paragraph 2). So, when paragraph 3 discusses how water in underground rock strata "does not flow entirely under the influence of gravity," we can see how liquid toxic waste might flow in a similar way, especially when it is mixed with water (which leads us to the 'uncertainty' mentioned in paragraph 4).

I hope this helps!!
Kate