Answer:
D
Explanation:
Only anarcho-capitalists believe that defense should be provided by private firms.
A more general approach is that there are primary and secondary functions in the state.
Primary functions are defense, legislation, judiciary, and so on. Basically this means that the state should provide public goods
Secondary functions might include non-public goods such as education, health, energy and so on.
A good rule of thumb is that when economist say "small" goverment they mean that it should only take care of it's primary functions