The value of one microcurie $=$ $.......$ disintegrations / second

$A$ 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

In the reaction $_{93}Np^{239} \xrightarrow{} _{94}Pu^{239} + (?)$,the missing particle is

Which metal is used in radiation shielding?

If uranium (mass number $238$ and atomic number $92$) emits an $\alpha$-particle,what are the mass number and atomic number of the product?

Which of the following has the maximum penetrating power?