O2 (oxygen) is a covalent compound
Oxygen and carbon dioxide travels to and from tiny air sacs in the lungs, through the walls of the capillaries, into the blood. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs.

Answer:
Unlike matter, as energy flows through an ecosystem in one direction, from photosynthetic organisms to herbivores to omnivores and carnivores and decomposers, less and less energy becomes available to support life.
Explanation:
Primary producers use energy from the sun to produce their own food in the form of glucose, and then primary producers are eaten by primary consumers who are in turn eaten by secondary consumers, and so on, so that energy flows from one trophic level, or level of the food chain, to the next.
Energy is acquired by living things in three ways: photosynthesis, chemosynthesis, and the consumption and digestion of other living or previously-living organisms by heterotrophs.
Living organisms would not be able to assemble macromolecules (proteins, lipids, nucleic acids, and complex carbohydrates) from their monomeric subunits without a constant energy input.
I think B but I maybe wrong please correct
Impact of the use of fossil fuels during the industrial revolution was it made possible a huge increase in the amount of productive energy available to humans.
The development of machines, including steam engines and the internal combustion engine, made it possible to exploit vast new resources of energy stored in fossil fuels, specifically coal and oil. The fossil fuels revolution greatly increased the energy available to human societies during industrial revolution.
Contrary to this fossil fuel have some disadvantages like when fossil fuels are burned, they release large amounts of carbon dioxide, a greenhouse gas, into the air. Greenhouse gases trap heat in our atmosphere, causing global warming.
To learn more about fossil fuel , here
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