Hydrogen is the ultimate building block in the stages of nuclear fusion inside stars, forming helium and subsequently heavier elements during the fusion process. It is the simplest and most abundant element in the universe, serving as the foundation for the creation of all other elements found in stars. The process of fusion allows for the progression from hydrogen to more complex elements like carbon and oxygen. ;
Hydrogen is the ultimate building block of nuclear fusion in stars, primarily fusing to form helium and subsequently heavier elements like carbon and oxygen. It is the simplest and most abundant element, making it crucial for stellar processes. As a result, the answer is A. hydrogen.
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