\eqalign{ & If\,\frac{a}{{b + c}}{\text{ = }}\frac{b}{{c + a}}{\text{ = }}\frac{c}{{a + b}}{\text{ = }}k{\text{,}} \cr & {\text{then the value of }}k\,{\text{is}} \cr} $$

• A. -1/2
• B. 1
• C. -1
• D. 1/2