pick someone up on something
phrasal verb with pick verb uk/pɪk/ us/pɪk/
在…上挑（某人）毛病，指出（某人）在…方面的错误
to criticize someone about something they have said
"I want to pick you up on the point you made a few minutes ago about personal morality, Archbishop." “大主教，我对您刚才有关个人道德的观点有不同的意见。”
His teacher picked him up on his pronunciation. 他的老师指出了他的发音错误。