题目

 Are you facing a situation that looks impossible to fix?  In 1969, the pollution was terrible along the Cuyahoga River near Cleveland, Ohio. It 61._________( be ) unimaginable that it could ever be cleaned up. The river was so polluted that it 62._________( actual) caught fire and burned. Now, years later, this river is one of 63.________ most outstanding examples of environmental cleanup.      But the river wasn’t changed in a few days 64.________ even a few months. It took years of work 65.___________( reduce ) the industrial pollution and clean the water . Finally, that hard 有理数3的相反数的倒数是________．