call
[误] I'll call at Mr Brown.
[正] I'll call on Mr Brown.
[误] I'll call on Mr Brown's home.
[正] I'll call at Mr Brown's home.
[析] 作"拜访"讲时,at后面接访问地点,而on后面接访问的人。
call on drop in visit
call on比较正式的为公务的访问,如:We were called on by the old students. 而drop in则是比较随便的走走,顺便拜访,如:If you're free, drop in. 而visit则是更正式的外交访问或友好往来,如:My school's headmaster will visit America next week.