根据要求改写句子。 1.He spent 10 yuan buying the pen . (改为同义句) He ___ 10 yuan __ the pen. 2.Finishing the work is hard . (改为同义句) _ hard _ the work. 3.Why not go shopping ?(改为同义句) _ shopping ? 4.If you aren't quick , you'll miss the bus . (改为同义句) _ , __ you'll miss the bus .