An electron (mass $9 \times 10^{-31} \ kg$ and charge $1.6 \times 10^{-19} \ C$) moving with speed $v = c/100$ $(c = 3 \times 10^8 \ ms^{-1})$ is injected into a magnetic field $\vec{B}$ of magnitude $9 \times 10^{-4} \ T$ perpendicular to its direction of motion. We wish to apply a uniform electric field $\vec{E}$ together with the magnetic field so that the electron does not deflect from its path. Then:

• A
  $\vec{E}$ is perpendicular to $\vec{B}$ and its magnitude is $27 \times 10^4 \ V \ m^{-1}$
• B
  $\vec{E}$ is perpendicular to $\vec{B}$ and its magnitude is $27 \times 10^2 \ V \ m^{-1}$
• C
  $\vec{E}$ is parallel to $\vec{B}$ and its magnitude is $27 \times 10^2 \ V \ m^{-1}$
• D
  $\vec{E}$ is parallel to $\vec{B}$ and its magnitude is $27 \times 10^4 \ V \ m^{-1}$