The correct answer is option A, the type of isotope
Explanation:
The half life of a radioactive substance is a constant value and thus it is not affected by the temperature, catalyst or mass of the substance. Basically it is the time taken by a radioactive substance to reduce its mass by half of its actual value. Radioactive decay takes place only when the atomic nucleus becomes unstable and thus the isotope type is the only factor which affects the radioactive decay of any element.
