Answer: Bog
Explanation: A bog can be defined as the wetland that accumulates peat (dead and decaying plant material) in water and remains still for longer duration of time. This is a type of wetland.
They are mostly covered by peat and sphagnum moss. The gradual accumulation of peat in the wetland makes it a carbon sink.
It is mostly formed when the ground surface is acidic and has very quantity of nutrients in it.