If tan θ = a/b such that \(\frac{asin~\theta ~-b\cos \theta }{a\sin \theta ~+~b\cos \theta }~=~{{\left[ \frac{{{a}^{2}}-{{b}^{2}}}{{{a}^{2}}+{{b}^{2}}} \right]}^{k}}\) , then k is:

• A. 6
• B. 2
• C. 1
• D. 8