1、Tom’s father joined the army in 1990.
Tom’s father（has）（been）（in）the army（for）23 years.
2、They arrived in Beijing two hours ago.
They（have）（been）（in）Beijing（for）two hours.
3、This stream became dirty last year.
This stream （has）（been）dirty（since）last year.
4、They left Fuzhou five years ago.
They （have）（been）（away）（from）Fuzhou（for）five years.
It （has）（been）five years（ever）（since）they （left）Fuzhou.
It （is）five years（since）they（left）Fuzhou.
5、They went to the U.S.A.in 2000 and 2005.
They （have）（been）（to）the U.S.A.（twice）.