Which of the following luminosity classes refers to stars on the main sequence?

Name: Which of the following luminosity classes refers to stars on the main sequence?
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Question

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Luminosity class V refers to stars on the main sequence, which means they are actively fusing hydrogen into helium in their core, the defining characteristic of main sequence stars. Luminosity classes I-IV refer to stars that have evolved away from this stage and are no longer on the main sequence.

Which of the Following Luminosity Classes Refers to Stars on the Main