Passage Summary: A plan to help one part of a river will hurt another part even more, so the plan is a net loss for the whole area.

Conclusion: Building a dam on the Merv River would result in no net increase in agricultural productivity for the entire region.

Reasoning: The dam would help one area but harm another, and the specific loss in productivity downstream would outweigh the productivity gains seen upstream.

Analysis: To find the parallel, we must abstract the structure: An action produces a benefit in one sub-sector but a larger deficit in another sub-sector, leading to a net negative or neutral outcome for the whole system. The logic is a simple 'cost-benefit' calculation where the costs are explicitly stated to be greater than the benefits. Look for an answer choice that follows this 'A helps X, but A hurts Y more, so A is bad for the total of X and Y' pattern. Avoid choices that focus on the environment or rivers specifically; focus instead on the math of the trade-off.