Final answer:
The United States agreeing to certain standards for the treatment of workers with other countries as a foreign policy tool is an example of diplomacy. Option B.
Step-by-step explanation:
When the United States and several other countries agree to certain standards for the treatment of workers as part of their foreign policy, this is an example of diplomacy. Diplomacy is the practice of conducting negotiations between representatives of states and is a key tool of foreign policy used by governments to engage in discussions and create agreements that advance their national interests and values. The goals of U.S. foreign policy include keeping the country safe, securing access to foreign markets, and protecting human rights.
International agreements can serve as a political counterweight to domestic special interests and can prevent stronger protectionist measures. Such agreements are part of nonmilitary tools, often considered as soft power, used by countries to influence the policies and behavior of other countries.