Which of the following is emitted, when ${ }_{94}^{239} Pu$ decays into ${ }_{92}^{235} U$?

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

Neutrino is a particle which $\qquad$

$A$ free neutron decays spontaneously into :

Consider the following two statements:
$A.$ The energy spectrum of $\alpha-$ particles emitted in radioactive decay is discrete.
$B.$ The energy spectrum of $\beta-$ particles emitted in radioactive decay is continuous.

$A$ nucleus of mass $218\, amu$ in a free state decays to emit an $\alpha$-particle. The kinetic energy of the emitted $\alpha$-particle is $6.7\, MeV$. The recoil energy (in $MeV$) of the daughter nucleus is: