结束用end还是ending
用end，例如：
1.By the end of the day we were tired but happy.一天结束时，我们很累，但很高兴。
2.I always leave a clear desk at the end of the day.每天工作结束时，我总是把桌上收拾干净不放任何东西。
3.The new model will be in production by the end of the year.新型号将于年底投产。
用end，例如：
1.By the end of the day we were tired but happy.一天结束时，我们很累，但很高兴。
2.I always leave a clear desk at the end of the day.每天工作结束时，我总是把桌上收拾干净不放任何东西。
3.The new model will be in production by the end of the year.新型号将于年底投产。