Answer:
D.) President agreeing to send troops to settle an international conflict
Step-by-step explanation:
Domestic policy refers to rules, regulations, strategies, etc. created by a government that primarily concerns their own country/citizens. These laws do not directly impact other nations.
A.) is incorrect because the President of the U.S. is approving a bill brought forth by the Congress of the U.S. While the bill's content may deal with foreign policy, this statement likely just concerns an American president interacting with his Congress and approving internal legislation.
B.) is incorrect because the HOR (House of Representatives) is an American entity proposing a new tax law on American citizens. This law concerns a particular government taxing its people.
C.) is incorrect because the U.S. Senate is introducing a proposal to help a U.S. state. Again, this policy would serve as a connection between the American government and an American state.
D.) is correct because sending a country's military to a foreign nation directly impacts international relations. This policy impacts the general American society, but the agreement is based on international politics.