Answer: b. Fossil fuels are a valuable energy source for the biosphere.
Explanation:
The living organisms are dependent upon the earth crust for their food and resource needs. The earth crust is mined for a variety of inorganic and organic reserves like minerals, fossil fuels like petroleum, gasoline, natural gas and coal. The fossil fuels are non-renewable resources which are produced after million's of years the complete degradation and decomposition of the organic matter of dead animals and plants. This act as source of energy by the living organisms in biosphere.
The complex eukaryotic cell ushered in a whole new era for life on Earth, because these cells evolved into multicellular organisms. Evidence supports the idea that eukaryotic cells are actually the descendents of separate prokaryotic cells that joined together in a symbiotic union.
