Aflood plain has the potential to flood. why is this a problem?
a. flood damage is extremely costly due to homes and businesses being built on the flood plain
b. floods are unnatural events caused by human activity
c. floods are caused by drought cycles in the weather
d. flood damage is permanent, causing major changes in the course of the bordering river channel
e. when flood waters recede, the flood plain is left infertile for growing crops

A. flood damage is extremely costly due to homes and businesses being built on the flood plain

Explanation:

Floodplain is a waterfront region that is flooded during floods. These areas are very suitable for agriculture due to soil fertility. Such areas develop over the gutter of a valley filled with alluvial soil, over which meanders meander due to the low slope of the river course, which, in flood times, spills over its original bank and floods the adjacent region.

Flooding in this region is natural, but because of the increase in population and the need for expansion of cities, many houses and industries needed to be built in the plains of inunction. In this case, the floods cause a major problem because they cause damage to homes and industries. These losses cause often incalculable economic and emotional damage.

a and b because with the other three, they simplify to something else.