The correct answer is: Only I and II follow.
The statement says that many private sector banks have reduced interest rates on housing loans in comparison to public sector banks. This means that public sector banks are at a disadvantage and may lose customers to private sector banks.
Course of action I says that the case should be raised before the regulatory authority for investigation by the public sector banks as they cannot follow such reduction. This is a valid course of action because it would allow the regulatory authority to investigate the matter and ensure that public sector banks are not being unfairly disadvantaged.
Course of action II says that public sector banks must adopt such policy to remain in competition. This is also a valid course of action because it would allow public sector banks to remain competitive and avoid losing customers to private sector banks.
Course of action III says that the public sector banks should advertise their special feature repeatedly so that they do not lose their future customers. This is not a valid course of action because it does not address the underlying issue, which is that public sector banks are at a disadvantage due to the lower interest rates offered by private sector banks.
In conclusion, only courses of action I and II follow.