Which of the following is not a radioactive isotope?
calcium-40
Explanation for the correct option
option(C):calcium-40 is a stable, non-radioactive isotope of calcium.
Explanation for the incorrect options.
option(A): carbon-14 is a radioactive isotope of carbon.
option(B): sodium-24 is a radioactive isotope of sodium.
option(D): iodine-131 is a radioactive isotope of iodine.
Hence option(C) is correct.Calcium-40 is a non radioactive isotope.