The ultimate source of energy for every cycle is

The correct answer would be the sun.

Explanation:

The sun is the ultimate source of energy for earth's biosphere. It powers all the cycles and food chains present on earth.

The solar energy is converted into chemical energy by the process termed as photosynthesis. This energy then transferred to higher trophic levels in any food chain.

Thus, it helps in cycling of different elements such as carbon throughout the biosphere.

Another example may include water cycle which starts with evaporation and transpiration of water from water bodies. The energy for the same is also provided by the sun.