What is the famous isotope used in archeological dating?

carbon 12

I thought it was carbon 14

yes

carbon 14-- made an error

But if you knew, why are you asking these questions?

I need reaasurance, so when I have a test I know the exact answer

C-14 is ONE of the radioactive isotopes used for dating. U/Pb is another. K/Ar is another. I have never heard anything about C-14 being "famous." The particular isotope used depends upon the age of the object to be dated. For example, C-14 has a half-live of about 5700 years which is useful for determining the age of fossils that are not too old (in the thousands/ten thoushands of years); however, it isn't useful for determining the age of really old old stuff (say the earth) with an age of several billion years.