At the age of fourteen,Bell 【sent 】to London to_was sent____
live for a year with his grandfather,【that 】 took good care _who____
of him.A year【 late】,young Bell returned to Scotland._later____
After working for 【 time 】with his father,he bagan teachinga_time____
speech at a school.His free time was devoted to【 study 】_studying___ _
sound.【Before】 he studied the human voice and the __After___
vibrations(振動(dòng))that 【goes】 to make up sound,he found that the_went____
voice was not a simple thing.So he continued【 on 】with his __刪掉___
studies and his teaching until at the age of【 tewnty-third 】 _twenty-three____
【 】he moved with his family to Canada. _when____