A, B are two events in a random experiment such that  $0<P\left(A\right)<1andP\left(B\right)\ne 1$ 
Assertion (A) :  $P\left(\frac{A}{B^C}\right)=\frac{P\left(A\right)-P(A\cap B)}{1-P\left(B\right)}$ 
Reason   (R) :  $P\left(\frac{A}{B}\right)=\frac{P(A\cap B)}{P\left(B\right)}$

Both A and R are true and R is the correct explanation of A

Both A and R are true and R is not the correct explanation of A

A is true and R is false 

A is false and R is true