For determining the support reactions at A and B of a three hinged arch, points B and Care joined and produced to intersect the load line at D and a line parallel to the load line through A at D’. Distances AD, DD’ and AD’ when measured were 4 cm, 3 cm and 5 cm respectively. The angle between the reactions at A and B is___________________?
A. 30°
B. 45°
C. 60°
D. 90°