No links please

Choose the correct answer from the given alternative :

  Qiv). A unit vector perpendicular to both the vectors $\hat{\mathrm{i}} +\hat{\mathrm{j}} \mathrm{and} \hat{\mathrm{j}} +\hat{\mathrm{k}} \mathrm{is} -$

      a) $\frac{1}{\sqrt{3}}\left(\hat{\mathrm{i}}+\hat{\mathrm{j}}+\hat{\mathrm{k}} \right)$      b) ​$\frac{1}{\sqrt{3}}\left(\hat{\mathrm{i}}-\hat{\mathrm{j}}+\hat{\mathrm{k}} \right)$   c) ​$\frac{1}{\sqrt{3}}\left(\hat{\mathrm{i}}-\hat{\mathrm{j}}-\hat{\mathrm{k}} \right)$ d) ​​​$\frac{1}{\sqrt{3}}\left(-\hat{\mathrm{i}}-\hat{\mathrm{j}}+\hat{\mathrm{k}} \right)$