A) $ -1 $
B) $ 1 $
C) $ 2 $
D) $ 4 $
Correct Answer: B
$ \Rightarrow $ $ x(x+1)=x+y+z $
$ \Rightarrow $ $ \frac{1}{x+1}=\frac{x}{x+y+z} $ (i) Similarly, $ \frac{1}{y+1}=\frac{y}{x+y+z} $ … (ii) and $ \frac{1}{z+1}=\frac{z}{x+y+z} $ … (iii) On addition Eqs. (i), (ii) and (iii), we get $ \frac{1}{x+1}+\frac{1}{y+1}+\frac{1}{z+1}=\frac{x}{x+y+z}+\frac{y}{x+y+z}+\frac{z}{x+y+z} $ $ =\frac{x+y+z}{x+y+z}=1 $