Question

The Venn diagram below shows some of the services provided by national and state governments.

Diagram showing two circles that overlap in the center. The circle on the left is labeled National Government and lists powers to make agreements with foreign nations, establish post offices and interstate highways, and to raise and support military forces. The circle on the right is labeled State Government and lists the powers to create local government, build and support public schools, and to organize and control trade within the state. The section of the diagram where the circles overlap contains a question mark.

Which service completes the Venn diagram?