Which of the following is a correct statement?

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

$A$ radioactive substance emits

$A$ radioactive nucleus is initially at rest. It decays by emitting an electron and a neutrino at right angles to each other. The momentum of the electron is $3.2 \times 10^{-23} \ kg \cdot m/s$ and the momentum of the neutrino is $6.4 \times 10^{-23} \ kg \cdot m/s$. What is the direction of the recoil of the nucleus with respect to the direction of the electron?

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

The particles emitted in the decay of $ { }_{92}^{238} U $ to $ { }_{92}^{234} U $ are: