For determining the support reactions at A and B of a three-hinged arch, points B and C are 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

$$ 30^\circ $$ 

B

$$ 45^\circ $$

C

$$ 60^\circ $$

D

$$ 90^\circ $$