In the following nuclear reaction,identify $x$: $_{29}Cu^{64} \to _{28}Ni^{64} + x$

Which is not emitted by a radioactive substance?

$A$ 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

$C_{6}H_{5}F^{18}$ is an $F^{18}$ radio-isotope labelled organic compound. $F^{18}$ decays by positron emission. The product resulting from the decay is:

The reaction $_5B^8 \to _4Be^8 + _1e^0$ is due to

Radioactive substances emit $\gamma$-rays,which are