If + - = k + 1 k - 1, then k = ?

Answer: Option B

$$\begin{array}{rl}& \frac{\tan \theta +\sin \theta }{\tan \theta -\sin \theta }=\frac{\text{k}+1}{\text{k}-1}\\ & \frac{\tan \theta }{\sin \theta }=\text{k}\\ & \text{k}=\sec \theta \end{array}$$