Why,even Though Interest Payments Are Not Specifically Listed as Mandatory

Why,even though interest payments are not specifically listed as mandatory spending in the federal budget,could they be considered mandatory?

A) They are considered mandatory spending because such payments are fixed at the time of borrowing and cannot be altered.
B) They are considered mandatory spending because the interest rates on federal debt are extremely high, and failing to pay accumulated interest would dramatically increase the total debt.
C) They are considered mandatory spending because not making such payments could cause the government to go into default, which could make it harder to borrow going forward.
D) They are considered mandatory spending because interest payments constitute the largest part of yearly government spending.
E) They are considered mandatory spending because most interest payments go to American households and those citizens depend on the interest payments for their livelihoods.