在特殊情况下 用英语怎么说

应该都可以.
in the circumstances例句
In the circumstances it was tactless to ask her age.
在这种特殊情况下问她的年龄是不得体的.
under circumstances例句
An unscheduled airplane landing that is made under circumstances (engine failure or adverse weather) not under the pilot's control.
特殊情况（发动机失灵或恶劣气候）下没有计划到的飞机着陆.