If\[a{{\sin }^{-1}}x-b{{\cos }^{-1}}x=c,\]then\[a{{\sin }^{-1}}x+b{{\cos }^{-1}}x\]is equal to

• A. 0                     
• B. \[\frac{\pi ab+c(b-c)}{a+b}\]
• C. \[\frac{\pi }{2}\]            
• D. \[\frac{\pi ab+c(a-b)}{a+b}\]