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