Which is the structure labeled a?

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

How energy flows through each level in this energy pyramid. is all the matter and energy from one level transferred to the next level?

What is the main fuel source for the work of the cell