Step 1: Understanding the Concept:
This question asks us to identify the rhetorical function of a specific phrase within the passage's argument. We need to analyze how this phrase relates to the ideas that come before it.
Step 2: Detailed Explanation:
The passage first introduces the general principle of using taxes to deal with "negative externalities." This is a broad economic concept.
The third sentence then becomes more specific: "Economics is precise about the tax that should, in principle, be levied to deal with negative externalities: the tax on a liter of fuel should be equal to the harm caused by using a liter of fuel."
The phrase in question takes the general idea of taxing externalities and applies it directly to the specific case of automobile fuel. It provides a concrete rule for how the general principle should be implemented in this particular context.
Analyzing the Options:
(A) It restates a point made earlier in the passage.
This is incorrect. The earlier points are more general; this phrase introduces a new, more specific idea.
(B) It provides the evidence on which a theory is based.
This is incorrect. The phrase is part of the theory or principle itself, not the empirical evidence supporting it.
(C) It presents a specific application of a general principle.
This is correct. The general principle is how to tax negative externalities, and the phrase describes the specific application to fuel taxes.
(D) It summarizes a justification with which the author disagrees.
This is incorrect. The author presents this as the correct, precise economic view. The author's disagreement is with any tax that is *too high*, not with this principle for setting the tax.
(E) It suggests that the benefits of a particular strategy have been overestimated.
This is incorrect. The phrase is about how to properly calculate the tax, not about whether the benefits of the tax are overestimated.
Step 3: Final Answer:
The phrase serves to apply the general economic principle of taxing negative externalities to the specific context of fuel consumption.