The answer is all of the above
The half-life of carbon-14 is equal to 5730 years. The amount of substance with half-life h at any time t is equal to,
At = (Ao) x (1 - 0.5)^(t/h)
Substituting,
At/Ao = 0.67 = 0.5^(t/5730)
The value of t from the equation is 3310.6 years.
She is more likely tp have it for about 50%
Gravitational.....................
