29. _____ practicing hard every day, Justin has been able to play the piano very well _____ he was t
問題詳情
29. _____ practicing hard every day, Justin has been able to play the piano very well _____ he was three. At the age offive, he played at a music festival for the first time. (A) By； before (B) With； when (C) By； since (D) With； after