Which among the following minerals contains a radioactive element?

Which of the following is the most stable atom?

The end product of the $4n$ series is:

Consider the following nuclear reactions:
$_{92}^{238}M \to _{y}^{x}N + 2_{2}^{4}He$
$_{y}^{x}N \to _{B}^{A}L + 2\beta^{+}$
The number of neutrons in the element $L$ is:

The phenomenon of radioactivity arises from the

Which element is the end product of each natural radioactive series?