68. An electron passes through an environment that contains a uniform magnetic field and a uniform electric field. If the magnitude and direction of the electron's velocity remain constant along this path, which statement is correct?
[(1)] Both fields are parallel to the path of the electron and in opposite directions.
[(2)] Both fields are perpendicular to the path of the electron and in opposite directions.
[(3)] The magnetic field is necessarily perpendicular to the path of the electron, but the electric field may not be perpendicular to this path.
[(4)] The electric field is necessarily perpendicular to the path of the electron, but the magnetic field may not be perpendicular to this path.
\textbf{68.} An electron passes through an environment that contains a uniform magnetic field and a uniform electric field. If the magnitude and direction of the electron's velocity remain constant along this path, which statement is correct?
\begin{enumerate}
\item[(1)] Both fields are parallel to the path of the electron and in opposite directions.
\item[(2)] Both fields are perpendicular to the path of the electron and in opposite directions.
\item[(3)] The magnetic field is necessarily perpendicular to the path of the electron, but the electric field may not be perpendicular to this path.
\item[(4)] The electric field is necessarily perpendicular to the path of the electron, but the magnetic field may not be perpendicular to this path.
\end{enumerate}