Nature of EM Waves & Wave Equation question from NEET 2021

Answer: (c)

1. Need $\vec{E}\cdot\vec{B} = 0$ and $\vec{E}\times\vec{B}$ along $+\hat{i}$.
2. (a), (b), (d): $\vec{E}\parallel\vec{B}$, so $\vec{E}\times\vec{B} = 0$. Rejected.
3. (c): $(-\hat{j}+\hat{k})\cdot(-\hat{j}-\hat{k}) = 1-1 = 0$.
4. $(-\hat{j}+\hat{k})\times(-\hat{j}-\hat{k}) = \hat{j}\times\hat{k} - \hat{k}\times\hat{j} = 2\hat{i}$, along $+x$.
5. So the answer is (c).