If b + c = ax, c + a = by, a + b = cz, then the value of \(\frac{1}{9}\left[ {\frac{1}{{x\; + \;1}} + \frac{1}{{y + 1}}\; + \;\frac{1}{{z\; + \;1}}} \right]\) is:

• A. 1
• B. 1/3
• C. 0
• D. 1/9