Amain sequence star becomes a after it uses up the hydrogen in its core.

If you search it on the internet, most likely, it would lead you to D as the answer. However, this is wrong. They only become giants after when the hydrogen used is less than 10%. Actually, this phase occurring has nothing to do with the hydrogen being used up. It is about the accumulation of Helium in the core.

The answer is cjust typing because the minimum is 20 bl bl bl