The correct option is A belief in the use of violent methods.
The writer is a firm believer in non-violence, as indicated by the final sentence. Therefore, when he states that India's acceptance of the "doctrine of sword" will be his "hour of trial", implies that 'doctrine of sword' must definitely be the exact opposite of his principles and faith, Therefore, the logical conclusion is that the expression 'doctrine of sword' must mean a belief in violence or violent methods (option A). The other choices do not fit the context.