In the given reaction sequence ${ }_z X^A \rightarrow{ }_{z+1} Y^A \rightarrow{ }_{z-1} K^{A-4} \rightarrow{ }_{z-1} K^{A-4}$,identify the radioactive radiations emitted in order.

$A$ hypothetical radioactive nucleus decays according to the following series:
$A \xrightarrow{\alpha} A_1 \xrightarrow{\beta^-} A_2 \xrightarrow{\alpha} A_3 \xrightarrow{\gamma} A_4$
If the mass number and atomic number of $A$ are respectively $180$ and $72$,then the atomic number and mass number of $A_4$ will be respectively:

Which of the following is deflected by an electric field?

Which one of the following cannot emit $\gamma$-radiation and why? $(i)$ Excited nucleus,(ii) Excited electron.

Statement-$1$: $A$ nucleus having energy $E_{1}$ decays by $\beta^{-}$ emission to a daughter nucleus having energy $E_{2}$,but the $\beta^{-}$ rays are emitted with a continuous energy spectrum having an end-point energy $E_{1} - E_{2}$.
Statement-$2$: To conserve energy and momentum in $\beta$ decay,at least three particles must take part in the transformation.

Outside a nucleus,which of the following statements is true?