Answer:
National level : President
State level : Governor
Local level : Mayor
Step-by-step explanation:
The leader of the executive branch has the power to enforce the laws that created by the legislative branch.
President has the highest authority in enforcing laws that affected the whole nation (such forming relationships with other countries, Federal tax, etc)
The governor has the highest authority in enforcing the law that affected the state (such as state tax income, legalities of a certain product, etc)
The Mayor has the highest authority in enforcing law that affected the local (such as allocating budgets to build local infrastructures or education curriculum)