When examining a country's "Debt-to-GDP" ratio, one must remember A. that debt is the stock variable, while GDP is the flow variable. B. the federal government is required to keep this ratio less than 1, so debt can only rise if GDP rises. C. that debt is the flow variable, while GDP is the stock variable. D. Since debt is a stock variable, and GDP is a flow variable, this number is always greater than 1