State the name of the radioactive isotope that has a half-life that is approximately the same as the estimated time of the origin of earth.

After reviewing the graph you posted above, there is one radioactive isotope that has a half life that is approximate to the same as the estimated time of the origin of Earth. 

The radioactive isotope is called Uranium 238. You can also write this out as U-238 or uranium/u. Any of these are acceptable for the answer. 

Dall of the above all of the choices make sense

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