The following sentences are the steps involved in proving the result `(cosx)/(1-tanx)+(sinx)/(1-cotx)=cosx+sinx`. Arrange them in sequential order from first to last.
A. `(cos^(2)x)/(cosx-sinx)+(sin^(2)x)/(sinx-cosx)`
B. `(cos^(2)x-sin^(2)x)/(cosx-sinx)`
C. `(cosx)/(1-(sinx)/(cosx))+(sinx)/(1-(sinx)/(sinx))`
D. (a) (A), (B) and (C)
(C), (A) and (B)
(C), (B) and (A)