Answer:
All of the given statements are true.
Explanation:
All the elements are heavier than Bismuth (Bi) are radioactive.
The time for half of the original sample to spontaneous decay is called half life ([tex]t_{1/2}[/tex])
[tex]t_{1/2}=\frac{ln\:2}{\lambda}\\\lambda\:is\:the\:radioactive\:decay\:constant[/tex]
All radioactive elements are spontaneously decaying towards formation of a stable element.
Radioactive elements undergo decay in order to attain stability.
Radioactivity is a natural part of our environment. The earth also contains several primordial long-lived radioisotopes that have survived to the present in significant amounts.
Hence, all the given statements are true.