Why do food chains in an ecosystem rarely contain more then five organisms

Why do food chains in an ecosystem rarely contain more than five organisms? ... Nutrients are lost from the ecosystem when organisms die. The conversion of food into growth by an organism is not very efficient. Energy is recycled by the decomposers back to the producers.

i think that c)gold was found there

but i am not sure

and after water is usually warmed by the sun the water temperature raises and then evaporates .