Radioactive isotopes decay at a regular rate, that's why they are useful in radioactive carbon- 14.
What are radioactive isotopes?
It is also known as radioisotopes, radionuclide, or radioactive nuclide.
It is the element whose neutrons and protons are unstable.
These are the elements who release radiation on breaking down.
They can be present in nature or in labs.
They are used in treatments and imaging tests.
Thus, the correct option is 1. Decay at a regular rate.
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