After the terrorist attacks on september 11, 2001, governments within the united states raised expenditures to increase security at airports. these purchases of goods and services are a. not included in gdp since the government collects taxes to pay for them. b. included in gdp only to the extent that the federal government, rather than state or local governments, paid for them. c. included in gdp since government expenditures on goods and services are included in gdp. d. not included in gdp since they do not represent production.