Answer:
The correct answer is D. The national debt is decreasing.
Step-by-step explanation:
National debt is called the set of debts that a given country owns to private external investors, other nations, buyers of domestic bonds, etc., that is, all the debts of that country.
These debts, logically, increase each time the government bids for new bonds or other financing instruments, which are acquired by investors. Therefore, if the government buys these bonds, logically the national debt will decrease.