Question

which subproblem must be addressed first when designing a water purification system for a developing community?

evaluating the environmental impact of the systems technology
educating and involving the community in using the new system
assessing the available water sources for suitability and quality
reducing the systems costs for affordable community adaption

Explanation:

When designing a water purification system, the first step is to know what water sources are available and their quality. Without assessing the water sources, other steps like evaluating environmental impact, educating the community, or reducing costs are less relevant as the core input (water) is not understood.

Answer:

assessing the available water sources for suitability and quality