The electric field of a plane electromagnetic wave is given by
vector E = E0 (x + y)sin(kz - ωt)
Its magnetic field will be given by
(1) (E0/C) (x - y)cos(kz - ωt)
(2) (E0/C) (x - y)sin(kz - ωt)
(3) (E0/C) (-x + y)sin(kz - ωt)
(4) (E0/C) (x - y)sin(kz - ωt)