1. He has been there.
2. He has been there for three years.
两句都是“他在那里呆过”,他现在还在不在那里?不知道。
句2加了个“for three years”, 仍然是他可能在那里,也可能不在那里
如果确定他现在不在那里,而只是去过那里,直接说,
He(went there and)stayed there (for three years).
要表示他现在很可能在那里,
He has been living there (for three years).
要100% 表示他现在在那里
He is now living there.
....