In a triangle ABC if following relations hold good, in which of the case(s) the triangle is a right angled triangle?
A) r2 + r3 = r1 - r
B) a^2 + b^2 + c^2 = 8R^2
C) if the diameter of an excircle be equal to the perimeter of the triangle
D) 2R = r1 - r
Note: r - inradius
R - circumradius
1, 2 ,3 are subscripts denoting different inradiuses