Answer:
the only one of these materials that allows studying processes of a very long period of time is Uranium 238
Step-by-step explanation:
In a radioactive material, half of the atoms decay each life period, in carbon 14 this period T = 5730 years, so for a time of 40,000 years there are 7 life periods, so there are very few atoms left without decomposing .
To study older samples, materials with a longer life period are needed, let's show the visa time
²³⁸U T= 4.5 10¹⁰ years
⁹¹Rb T = 58 s
¹³¹I T= 8.04 days
⁶⁰Co T= 5.27 years
Therefore, the only one of these materials that allows studying processes of a very long period of time is Uranium 238