Carbon-14 is the typical radioisotope used to date materials; however it has limitation to 4 years a scientist who wants to date materials older than 4 years would most likely use
a. uranium- 238
b. rubidium- 91
c. iodine- 131
d. cobalt- 60

The answer would be Uranium-238

Explanation:

It's the only one that lasts longer than 40,000 years

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.

explanation: it gains negative electrons, therefore becoming negatively charged. as charge cannot be created, nor destroyed, only transferred, this leaves the wool positive. now that they have opposite charges, the two items attract.