Correct Answer: Mandatory spending is required by law, while discretionary spending is optional

Solution : The correct answer is (a) Mandatory spending is required by law, while discretionary spending is optional.

Mandatory spending refers to government expenditures that are required by law or statute. These spending obligations are typically established by legislation and include programs such as Social Security, Medicare, Medicaid, and interest payments on the national debt. The government does not have discretion over the allocation of funds for mandatory spending, as it is legally obligated to make these payments.

It's important to note that while mandatory spending is required by law, it does not necessarily mean that discretionary spending is "optional" in the sense of being nonessential. Discretionary spending is subject to policy priorities and political decisions, but it is still an integral part of the government's overall budget and resource allocation.