In urban areas, there are more people, therefore not a lot of farmland. (that eliminates C) If city buildings don't allow flood waters to recede, that could be dangerous in many ways. (So A is still a reasonable answer) If most cities are built in flood zones, there should be some form of shelter if houses aren't safe. Pollutants and diseases being carried in water are already dangerous, but easier to spread with rapid flood waters that are sweeping everywhere. So your best answer would be either A or B.
The three Rs in boaters' responsibility for the environment are: Reduce, Reuse, and Recycle
Since you asked me to explain one of them, I will explain the "reuse"
Boaters have the environmental responsibility to only carry reusable items (such as plates, cups, or silverware) when they're sailing. This will prevent any form of waste from being thrown out into the water.
Well, don't hang me if I'm wrong, but judging from the map I saw, I would say B.
