\textbf{201-} Which statement is correct?
\begin{enumerate}
\item Most isotopes of known elements are unstable.
\item In the ion ${}^{+}\text{Li}^{Y}$, the number of electrons equals the number of neutrons.
\item Chlorine atoms are mostly formed by their heavier isotopes.
\item If the atomic mass of element ${}^{Y}\text{C}$ is $2.33$ times the atomic mass of ${}^{1}\text{H}$, its atomic mass is $16\,\text{amu}$.
\end{enumerate}