来自蔡永泉的问题
【hasbeendoing还是hasdoneshelovesherstudents,———————————————allhertimeforthepastthreeyears.答案是hasdevoted我写的hasbeendevoting】
hasbeendoing还是hasdone
shelovesherstudents,———————————————allhertimeforthepastthreeyears.答案是hasdevoted我写的hasbeendevoting

