Question

Read the passage below carefully:

For decades, traditional Adire textile production in Abeokuta, Nigeria, has relied on synthetic indigo dyes and chemical fixatives that create toxic effluent. Local artisans routinely discharge untreated wastewater directly into adjacent streams, contaminating groundwater supplies and damaging local aquatic ecosystems. While mechanical water treatment plants offer a high-volume industrial solution, their exorbitant operational costs and reliance on unstable electrical grids render them impractical for informal dye cottage clusters. To address this environmental hazard sustainably, environmental engineers have introduced low-cost constructed wetlands utilizing native vetiver grass and gravel bio-filters. These artificial wetlands naturally absorb heavy metals, neutralize pH levels, and break down organic pollutants before water reaches public waterways. Pilot projects demonstrate that community-managed wetlands reduce biological oxygen demand by over eighty percent at a fraction of municipal utility costs. Furthermore, harvesting mature vetiver leaves provides local artisans with supplementary raw materials for weaving mats, generating secondary revenue. Consequently, decentralized biological filtration systems represent the most viable strategy for mitigating artisan dye pollution while preserving cultural heritage.

Based on the passage, match each of the excerpted statements with its correct functional role in the author's summary argument.