3、How long have you been studying English?
你学英语多久了?
4、How long a stay did you have in mind?
你原打算待多长时间?
5、How long have they been at war?
他们交战有多长时间了?
6、How long has he been in office?
他任职多久了?
7、It's difficult to judge how long the journey will take.
很难估计这次旅行要花多长时间。
8、The key is, how long can the federal government control the inflation rate?
关键在于联邦政府对通货膨胀率的控制能维持多久?
9、How long have Tom and Lucy been going out together?
汤姆和露西相恋多久了?