3. (5%) Which of the following staternents is correct?
(A) In a closed economy, introducing a pay-as-you-go social security system increases the incentive of saving,thereby raising the capital stock.
(B) In equilibrium, an increase in the marginal tax rate on labor income increases the demand for capital.
(C) An increase in the marginal tax rate on asset income reduces investment in the short run and therefore reducesreal GDP in the long run.
(D) The average income tax is the change in income taxes when income changes one dollar.