Help with Earth Science 11 (Astronomy)?

Fill in the blanks. Thanks!

In a stable star, the contraction due to gravity and the expansion due to nuclear fusion are "BLANK"

Once a star loses much of the "BLANK- I think it might be nuclei" atoms in the core, which are replaced by "BLANK- I think it might be layers," it loses its "BLANK- I think it might be stability." The star expands and becomes a "BLANK- I think it might be Red Giant.
 
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