Which of the following powers is held only by the federal government
a. power to make a treaty
b. power to set marriage laws
c. power to create driving laws
d. power to set the legal drinking age

The correct answer is A) power to make a treaty.

The power that is held only by the federal government is the power to make a treaty.

Under the Constitution of the United States, it is the President who can sign foreign treaties, but he needs the advice and the consents of the Senate to make those treaties. Any treaty must be approved by two-thirds of the Senate. The Senate also rejects or approves a resolution for the ratification of a treaty.