Answer: Polychlorinated biphenyls (PCBs) are a group of manmade chemicals. They are oily liquids or solids, clear to yellow in color, with no smell or taste. PCBs are very stable mixtures that are resistant to extreme temperature and pressure. PCBs were used widely in electrical equipment like capacitors and transformers. They also were used in hydraulic fluids, heat transfer fluids, lubricants, and plasticizers. The primary company that made PCBs in the United States was Monsanto Inc., mainly using the name Aroclor. Commercial production of PCBs ended in 1977 because of health effects associated with exposure. In 1979, the U.S. Environmental Protection Agency (USEPA) banned the use of PCBs; however, PCBs are still present in many pre-1979 products.
This is most likely the result of OXIDATION. When an apple is cut open, the cells of the apple are exposed to the atmosphere, the in built defense mechanism inside the apple that is supervised by certain enzymes react to this situation by reacting with oxygen and creating an oxidized brown layer which protects the apple from foreign bodies.
The structure of the ear that conducts sound waves to the middle ear is the oval window.
This is supposed to be a personal opinion answer.
The one that was so momentous about the "twofold" some portion of the twofold helix atom is it proposed how hereditary data could be replicated and acquired. Double helix is a long, straight atom made of littler units called nucleotides that shape a chain.