There are two hinged semicircular arches A, B and C of radii 5 m, 7.5 m and 10 m respectively and each carries a concentrated load W at their crowns. The horizontal thrust at their supports will be in the ratio of_______________?
A. 1 : 1½ : 2
B. 2 : 1½ : 1
C. 1 : 1 : 2
D. None of these