\[\frac{x}{1-x}+\] \[\frac{y}{1-y}+\] \[\frac{z}{1-z}=1\]then, find \[\frac{1}{1-x}+\]\[\frac{1}{1-y}+\]\[\frac{1}{1-z}=?\]

• A.  1    
• B.  2    
• C.  3     
• D.  4