it is the equator, as areas around it are the hottest parts of the earth.
the correct answer is a delta.
the formation of deltas takes place when a river meets a sea or the lake, at this moment, the speed of water becomes less and it loses the intensity to carry sediment. the sediment gets accumulated at the mouth of the river. some of the rivers leave so much of sediment that even the tides and waves become inefficient in carrying it all through. it accumulates in layers producing a delta. some of the deltas are so big that even humans can live on them.