Answer: A. The national debt increases by $500 billion.
Explanation:
National debt simply refers to the total debts that is owed by a particular country. Budget deficit on the other hand, has to do with a scenario whereby the proposed expenses by the government for a particular year is more than its revenue.
Regarding the question, if the government has a $500 billion budget deficit, this will lead to a rise in the national debt as the debt will increase by $500 billion as well.
Therefore, the correct option is A