Answer:
c
Step-by-step explanation:
While standing water in the streets and sewers (option A) and poor water quality in rivers and streams (option D) may persist for some time after the flood, they are generally considered short-term changes as they can eventually be remedied through clean-up efforts and restoration programs.
Temporary displacement of organisms (option B) can also be considered a short-term change, as organisms will eventually return to their original habitats once conditions improve.
However, a permanent change in the landscape (option C) such as altered river channels, new water bodies, or changes in topography, can have lasting effects on the ecosystem and its inhabitants. These changes may alter habitat suitability, nutrient cycling, and water availability, which can impact the ecosystem for years or even decades to come.