$A$ nuclear reaction is given by ${}_{Z}X^{A} \to {}_{Z+1}Y^{A} + {}_{-1}e^{0} + \bar{\nu}$,which represents:

The most penetrating radiation out of the following is

Neutron decay in free space is given as follows:
$_0n^1 \to _1H^1 + _{-1}e^0 + [\,\,]$
Then the particle in the bracket is:

Assertion: ${}_{Z}{X^{A}}$ undergoes $2\alpha$-decays,$2\beta$-decays,and $2\gamma$-decays,and the daughter product is ${}_{Z-2}{X^{A-8}}$.
Reason: In $\alpha$-decays,the mass number decreases by $4$ and the atomic number decreases by $2$. In $\beta$-decays,the mass number remains unchanged,but the atomic number increases by $1$.

Obtain the maximum kinetic energy of $\beta$-particles and the radiation frequencies of $\gamma$-decays in the decay scheme shown in the figure. You are given that:
$m(^{198}Au) = 197.968233 \; u$
$m(^{198}Hg) = 197.966760 \; u$

Radioactivity is a/an ...... process.