Answer: B
\(xz = y(\csc\theta + \cot\theta) \cdot y(\csc\theta - \cot\theta)\) ⇒ \(xz = y^2(\csc^2\theta - \cot^2\theta)\) ⇒ \(xz = y^2\) .
\(xz = y(\csc\theta + \cot\theta) \cdot y(\csc\theta - \cot\theta)\) ⇒ \(xz = y^2(\csc^2\theta - \cot^2\theta)\) ⇒ \(xz = y^2\) .