John is really expert at fighting cyber-crime!—Yes, but he _____ his potential if it had not been for his desire to meet the new challenge.[ ]

Mr Smith, _____ of the _____ speech, started to read a novel. [ ]

My sister________home at 5:00 every day．

I dislike those programs ______ viewers call in to talk about their private problems

ford English Dictionary is necessary for learning English, so you’d better buy ___.