\eqalign{ & \frac{1}{{1 + {x^{\left( {b - a} \right)}} + {x^{\left( {c - a} \right)}}}} + \cr & \frac{1}{{1 + {x^{\left( {a - b} \right)}} + {x^{\left( {c - b} \right)}}}} + \cr & \frac{1}{{1 + {x^{\left( {b - c} \right)}} + {x^{\left( {a - c} \right)}}}} = ? \cr} $$

• A. 0
• B. 1
• C. xa - b - c
• D. None of these
• E. None of these