Заполните пробелы правильной формой глагола: 1. taxation (have been, has been) one of the most prominent and controversial topics in economic policy. 2. taxes (has been, have been) levied by the federal and local authorities. 3. the most usual taxes (are, is) sales taxes, individual income taxes, and property taxes. 4. simplicity (means, mean) that relations of the taxpayer and the revenue authorities are as easy as possible. 5. taxes always (affect, affects) behavior. 6. the most efficient tax (are, is) a head tax. 7. the problem, though, (are, is) how to judge whether two taxpayers are equally situated. 8. revenue sufficiency might (seems, seem) a fairly obvious criterion of tax policy. 9. intricate legal provisions would also (make, makes them more complex. 10. such conflicts among policy objectives (is, are) a constant constraint on the making of tax policy.