The electric field for a plane electromagnetic wave travelling in the $+y$ direction is shown in the figure. Consider a point where the electric field is in the $+z$ direction. The magnetic field $\vec B$ is

• A
  in the $+x$ direction and in phase with the electric field $\vec E$
• B
  in the $-x$ direction and in phase with the electric field $\vec E$
• C
  in the $+z$ direction and in phase with the electric field $\vec E$
• D
  in the $-z$ direction and in phase with the electric field $\vec E$