Answer:
b. when the president vetoes congress's appropriations bills
Explanation:
A president can be defined as an individual who is duly elected by the electorates and as such is the head of the country in a democratic government. The president is empowered by the constitution to sign (veto) legislations, adjourn or convene the legislative body (Congress), grant state pardons and reprieve to citizens, command the armed forces, and welcome ambassadors representing other countries.
In the United States of America, the president has various powers granted by Acts of Congress and Article II of the U.S constitution such as Ordinance power, Appointment power, Implied power, Executive power, etc.
An appropriation bill comprises of proposed law by the legislature that gives the government of a particular country the authority to fund certain projects with a concise description of what the funds are to be used for.
In the United States of America, a government shutdown would arise when the US Congress fails to pass an appropriation bill so as to finance the government for the next fiscal year or when the president vetoes appropriations bills passed by the Congress.
Hence, when the president vetoes congress's appropriations bills, it will lead directly to a government "shut down."
