The correct answer is (b) Levees prevent rivers from flooding their banks.
Levees are formed when water pushes the sediments to the side of a river. They serve as a natural barrier and prevents flood. This is very beneficial in terms of human settlement. Levees can be natural or artificial. They prevent water from going into the areas where there is a human settlement (bank of river). They prevent the rivers from flooding cities in a storm surge. If levees are broken the result can be disastrous for the surrounding area.