<u>Answer: </u>The correct answer is Option D.
<u>Explanation:</u>
Unstable isotopes are defined as the isotopes which have excess of neutrons as compared to the stable form of the nucleus of an atom.
These isotopes attain stability by undergoing a spontaneous nuclear decay. The isotopes which are unstable have another name and are known as radioactive isotopes or radioisotopes.
These isotopes undergoes decay by 4 processes: Alpha decay, beta decay, gamma emission and positron decay.
Hence, the correct answer is option D.

Airbags are good for car crashes and have saved lots of life’s, the force of the airbags are dangerous though because they come out with fast acceleration and when it is hot it can burn you. If there is ever a time for collision airbags may save your live!
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The answer to your question is frequency.
If you would like further information about the subject, private message me and id be happy to explain in further detail for you!. :0