i think it is 8. I might be wrong.
Ice floats after it crystallizes because ITS DENSITY IS LESS THAN THAT OF WATER.
When a quantity of water is cools down by reducing its temperature, the molecules of the water lose kinetic energy and slow down in their movement. As the water is cooling down, it is volume is expanding. When the temperature reaches zero degree Celsius, the water becomes ice. At this point, the ice can float on water because its density is less than that of water; this is as a result of the spaces that now exist in the ice structure.
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the plants would grow and reproduce working together forming nutrients from their dropped leaves / branches etc causing insects to come along and do the same along with animals and a keystone species to form a revolving ecosystem continuing an energy moving process