The only false statement from the options is that the half-life of C-14 is 40,000yrs.
The half-life of an isotope is the time it takes for half of a radioactive material to decay to half of its original amount. C-14 has an half-life of 5730yrs. This implies that during every 5730yrs, C-14 will reduce to half of its initial amount.
All living organisms contain both stable C-12 and the unstable isotope of C-14
The lower the C-14 compared to the C-12 ratio in an organism, the older it is.
