An electron is moving along positive $x$-axis. A uniform electric field exists along negative $y$-axis. What should be the direction of the magnetic field (constant) so that the force on the electron is zero?

Question

$\begin {array} {1 1} (a)\;Positive \: y-axis & \quad (b)\;Negative\: y-axis \\ (c)\;Positive \: z-axis & \quad (d)\;Negative \: z-axis \end {array}$