Concession is appropriate because regulators hesitated despite the promising results. The other options imply causation, simple addition, or timing rather than acknowledging a contrast to expectations.

Moreover adds another piece of supporting evidence consistent with the first sentence. By contrast suggests opposition, Consequently implies a result rather than another support, and Even so introduces concession, none of which fit.

Concession fits because the second sentence acknowledges limitations while maintaining the initial claim's context. Therefore and By contrast imply causation or full opposition, and Moreover merely adds information without signaling a caveat.

Even so signals concession: despite grim predictions, the project advanced quickly. Therefore implies causation, Additionally suggests mere addition, and In contrast sets up a comparison rather than acknowledging the prior claim and defying it.

However introduces a contrast between lab success and real-world setbacks. The other choices suggest causation, simple addition, or a time shift, none of which capture the reversal.

Concession: despite extensive retraining, audits still found disparities, so 'Even so' signals a counterexpectation. The other choices indicate addition, causation, or a simple juxtaposed contrast, not a concession to an unexpected result.

Contrast: the second sentence challenges the prevailing interpretation by contrasting site conditions that hinder preservation. The other choices imply cause, similarity, or concession, none of which precisely signals this corrective contrast.

Contrast: the newer approach differs fundamentally from the older strategy, so 'By contrast,' is apt. The other options suggest cause/effect, simple addition, or concession, none of which captures the direct comparison.

Time/simultaneity: districts are acting at the same time researchers improve models, so "Meanwhile" is appropriate. The other options imply causation, contrast, or addition rather than concurrent developments.

Time/sequence: the second sentence describes earlier efforts, so 'Previously' correctly sets the chronology. 'However' (contrast), 'As a result' (cause/effect), and 'Moreover' (addition) misstate the connection.