Which of the following isotopes of uranium is the most radioactive?

During $\beta$-decay:

$A$ radioactive nuclide $X$ decays at the rate of $1.00 \times 10^5 \ disintegration \ s^{-1} \ g^{-1}$. Radium decays at the rate of $3.70 \times 10^{10} \ disintegration \ s^{-1} \ g^{-1}$. The activity of $X$ in millicuries $g^{-1}$ $(mCi \ g^{-1})$ is

After the emission of one $\alpha$-particle followed by one $\beta$-particle from the atom of $_{92}X^{238}$,the number of neutrons in the atom will be

If $_{92}U^{236}$ nucleus emits one $\alpha$-particle,the remaining nucleus will have

In the radioactive decay $_{92}X^{232} \to _{89}Y^{220}$,how many $\alpha$ and $\beta$-particles are ejected from $X$ to form $Y$?