191. The figure below shows a transverse wave on a string. Which of the following statements about points $M$ and $N$ on the string is correct? [Figure: A transverse wave on a string with $u_y$ axis vertical and $x$ axis horizontal; points M and N are marked on the string, with velocity vector $V$ shown at one point.]
[(1)] Their speeds are equal at every moment.
[(2)] They have equal amplitudes and frequencies.
[(3)] They are in opposite phase.
[(4)] They are in phase.
\textbf{191.} The figure below shows a transverse wave on a string. Which of the following statements about points $M$ and $N$ on the string is correct?
\textit{[Figure: A transverse wave on a string with $u_y$ axis vertical and $x$ axis horizontal; points M and N are marked on the string, with velocity vector $V$ shown at one point.]}
\begin{itemize}
\item[(1)] Their speeds are equal at every moment.
\item[(2)] They have equal amplitudes and frequencies.
\item[(3)] They are in opposite phase.
\item[(4)] They are in phase.
\end{itemize}