I. назовите три основные формы следующих глаголов: to leave, to put through, to clear up, to export, to think, to let, to ship, to require, to go, to have, to get, to find, to swim, to spend, to hear, to listen, to sell, to buy, to bring, to come, to speak.

to leave, left, left, to put put put through, to clear cleared cleared up, to export, exported, exported, to think, thought, thought, to let, let, let, to ship, to require, required, required, to go, went, gone, to have, had, had, to get, got, got, to find, found, found,  to swim, swam, swum, to spend, spent, spent, to hear, heard, heard, to listen, listened, listened,  to sell, sold, sold,  to buy, bought, bought, to bring, brought, brought, to come, came, come, to speak, spoke, spoken.