Answer:
Positive externalities are encouraged by subsidizing them so that they increase the more.
Negative externalities are punished by regulation and taxation to discourage their spread.
Public goods need to be provided because everyone needs access to them and not just a select few.
Monopolies have been shown to be inefficient as they do not have any competition that inspires innovation.
It is a government's duty to ensure that the country is experiencing certain macro economic goals such as low unemployment, strong growth and economic stability.
Note: Options were too much to attach to answer as they required multiple pictures so I hope you have access to those options.