18. which of the following is not correct about floodplains? they have recurrent problems with flooding the streams have natural levees adjacent to them othey are generally low-lying areas they are characterized by rapids and waterfalls

The statement that they are characterized by rapids and waterfalls is incorrect about floodplains.

Explanation:

All other points mentioned holds for flood plains:

Most of the floodplains are low lying areasThey are generally, the land areas which are adjacent to streams and riversThey are subjected to repeated influx or flooding.They can be simply characterized by a relatively smooth land area on whose boundary lies water stream or river which overflows or results in flooding at the time when water is high.

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.

Dis the answer you perception is how you see the world