In the emission of $\gamma$-rays from a nucleus:

If $_{92}U^{238} \to _{Z}X^{A} + _{2}He^{4}$,then $Z$ and $A$ will be ..........

The energy spectrum of $\beta$-particles [number $N(E)$ as a function of $\beta$-energy $E$] emitted from a radioactive source is

When an element ${}_{90}^{232}Th$ decays into ${}_{82}^{208}Pb$, the number of $\alpha$ and $\beta^{-}$ particles emitted respectively are

Which of the following processes represents a gamma-decay?

$A$ radioactive nucleus undergoes a series of decays according to the scheme
$A \xrightarrow{\alpha} A_1 \xrightarrow{\beta} A_2 \xrightarrow{\alpha} A_3 \xrightarrow{\gamma} A_4$
If the mass number and atomic number of $A$ are $180$ and $72$,respectively,then what are these numbers for $A_4$?