At What Point in the Budgetary Cycle Does an Agency

At what point in the budgetary cycle does an agency record a decrease (a debit) to the account "Allotments - realized resources"?

A) When the Office of Management and Budget makes an apportionment.
B) When the Department makes a quarterly allotment to the agency.
C) When the agency uses commitment accounting and makes a commitment for supplies.
D) When the agency uses supplies from its inventory.