Answer:
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 areas
- They are generally, the land areas which are adjacent to streams and rivers
- They 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.
C: the italian peninsula
see this map:

Photosynthesis is a process by which phototrophs convert light energy into chemical energy, which is later used to fuel cellular activities. The chemical energy is stored in the form of sugars, which are created from water and carbon dioxide.
A steppe is a large expanse of grasslands and few trees. So the choice of grassland with few trees would be your answer.
Good luck :)