Multiple choice

During which stage of a star's life cycle does it begin to fuse hydrogen into helium ?

  1. protostar

  2. white dwarf

  3. giant and supergiant

  4. main-sequence
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D Correct answer
Explanation

Stars spend the majority of their lives in the main-sequence stage, during which they fuse hydrogen into helium in their cores. Protostars are still forming, while giants and white dwarfs are later stages of stellar evolution.

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