A Scientist Claims That All Red Main- Sequence Stars Are

A scientist claims that all red main- sequence stars are 1 billion years old. Which of the following, if true, would prove that this claim is false?

A) Stellar evolution theory predicts that the main- sequence lifetime of red stars can be as long as 100 billion years.
B) The minimum lifespan of a red main- sequence star is estimated to be 10 billion years.
C) The discovery of a red main- sequence star in a star cluster where all the other stars are red giants or red supergiants
D) The discovery of a red main- sequence star in a star cluster where the main sequence turnoff is about that of the Sun