Federal responsibilities include: (multiple answers are possible) [mark all correct answers]
a. Providing national security
b. Ensuring that flying is safe
c. Ratifying amendments to the Constitution
d. Making and distributing money

The correct answers are A, B and D. Federal responsibilities include providing national security, ensuring that flying is safe, and making and distributing money.

Explanation:

The primary task of the federal government is to provide security for the people of the United States. Thus, through the Department of Homeland Security and the Department of Defense, the federal government seeks to protect its citizens from any external (from other countries) or internal threat, such as terrorism or violent actions. These Departments in turn organize both the armed forces and the police and security forces at the federal level, which are in turn complemented by the states.

Regarding security on flights and airports, this function is exercised by the Transport Security Administration, a federal agency that is in charge of security checks and preventive measures on the nation's planes, trains and other means of transportation.

Finally, the organization and administration of the monetary system also corresponds to the federal government, which exercises it through the Federal Reserve, which acts as the central bank of the United States and guides monetary policies and the creation of money throughout the country.