A- valve replacement
b- stents
x- heart transplant
Answer:
If your just looking for a description here you go.
Explanation:
Most spiral galaxies contain a central bulge surrounded by a flat, rotating disk of stars. The bulge in the center is made up of older, dimmer stars, and is thought to contain a supermassive black hole. Approximately two-thirds of spiral galaxies also contain a bar structure through their center, as does the Milky Way.
Hope this helps.
Answer:
It enters the atmosphere through both natural and human sources. Natural resources can be for instance volcanic eruptions, bacterial processes, evaporation from water, or decaying organisms. ... Sulfur dioxide may also react with water to produce sulfuric acid (H2SO4).
Explanation:
