The city of Curitiba was able to eliminate virtually all of the flooding of homes in low-elevations sectors of the city by ________
(a) Relocating residents and turning the floodplains into parks
(b) Hardening the storm sewer system so that rainwater that entered the storm sewers was rapidly routed downstream of the city
(c) Building a system of underflow tunnels into which stormwater was routed and then subsequently treated and recycled to irrigate parks
(d) Straightening the previously meandering streams so that runoff water that entered the streams did not back up.