The points $(a, b+c) , (b, c+a) $ and $(c,a+b)$ ________

Question

$\begin{array}{1 1}(A) \;are\;collinear\\(B)\;form\;an\;equilateral\;triangle \\(C)\;form\;an\;isosceles \;triangle \\(D)\;form\;a\;right\;angle\;triangle \end{array}$