The Magnetic Field of a Plane-Polarized Electromagnetic Wave Moving in the Z-Direction

Multiple Choice

The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by
$B = 1.2 \times 10 ^ { - 6 } \sin \left[ 2 \pi \left( \frac { z } { 240 } - \frac { t \times 10 ^ { 7 } } { 8 } \right) \right]$
in SI units.What is the wavelength of the EM wave?

A) 120 m
B) 240 m
C) 60 m
D) 100 m
E) 360 m