Freshwater ecosystems include three general categories: rivers and streams, lakes and ponds, and freshwater wetlands. Which of the following describes freshwater wetlands, but not the other two categories? Select all correct answers.
A. The ecosystem soaks up heavy rainfall, which helps to prevent flooding.
B. Water flows in one direction only through the ecosystem.
C. Water may cover the soil or lie just under the surface, for at least part of the year.
D. The ecosystem may be a freshwater bog, a marsh, or a swamp.