Which choice best describes the overall structure of the text?

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The establishment of urban green spaces for the abatement of fine particulate matter and other major air-pollutant concentrations is gaining public support, but urban planners must proceed with caution given subtleties in the body of evidence for the strategy’s efficacy. High-level reports have attributed pollutant reductions to cities’ inclusion of green spaces; however, one study found that while trees are negatively associated with air pollutants when considered on a citywide scale, at the street level, this association is minimal and at times positive. Because research tends to focus on large-scale effects in cities, decision-makers may be unaware that those outcomes are not always generalizable across spatial scales.

It outlines a problem that is of growing public concern, explains why an innovative solution to that problem is challenging to implement, and then suggests the importance of researching alternative solutions.

It addresses an appealing approach to a prevalent problem, illustrates that the approach is not as uniformly successful as it may seem, and then further emphasizes the importance of recognizing nuances in the research on that approach.

It details an initiative implemented in response to certain research findings, identifies an apparent inconsistency within those findings, and then explains how that inconsistency has typically been accounted for.

It establishes the growing intensity of a public concern, details the most common method of mitigating that concern, and then refers to evidence that the method is broadly ineffective.