The correct answer is: a) Civil service.
The Chief Secretary is the head of the state’s civil service. The civil service is the body of non-elected officials who carry out the day-to-day operations of a government. The Chief Secretary is responsible for overseeing the work of the civil service and ensuring that it is efficient and effective.
The Legislative branch is the branch of government that is responsible for making laws. The Judiciary is the branch of government that is responsible for interpreting laws. The Military is the branch of government that is responsible for defending the country.
The Chief Secretary is not the head of any of these branches of government.