The Energy of an Electron Is 100eV When It Enters

Multiple Choice

The energy of an electron is 100eV when it enters an E * B velocity selector that utilizes a cross electric and magnetic field to produce a zero net force on the particle. The magnitude of the magnetic field is 0.085T. The magnitude of the electric field required to produce a straight-line trajectory is

A) 5.0 *10⁴ V/m.
B) 2.5 * 10⁵ V/m.
C) 5.0 * 10⁵ V/m.
D) 2.5 * 10⁶ V/m.