Answer:
I think it is ether B or C
Hope this helps, please tell me if I am wrong
can u msg me, I have a few questions!
Answer: It was obtained 8515 years ago
Explanation:
Expression for rate law for first order kinetics is given by:

where,
k = rate constant
t = age of sample
a = let initial amount of the reactant
a - x = amount left after decay process
a) to find the rate constant:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.


b) for completion of 36% of reaction


t = 8515 years
The time was 8515 years.
Speed = frequency x wavelength
100 x 0.2 = 20
Fossils , silicone just guessed sorry