has been to 曾经去过某地,现在已经回到原地.它只能与表示次数的词语搭配,如：
She has been to Beidaihe twice.（此时不在北京）
How many times have you been to London?
has been in 表示一直呆在某地,常与时间段搭配,如：
She has been in Beijing for nearly two weeks..（此时仍在北京）
How long have you been in the factoory?