In 1963 a Lancaster bomber crashed on Wallis Island, a remote place in the South Pacific, a long way west of Samoa. The plane wasn't too badly damaged, but over the years, the crash was forgotten and the wreck remained...
... They point out that the main impact of two, such as atmospheric pollution and energy consumption are the direct or indirect results of the cheap air travel .They say that cheap airlines in order to save the cost of flying, no longer provide food and drinks to the passengers, no longer provide books...
Raise your hand if you had never heard of Tetralogy of Fallot with pulmonary atresia before Monday's episode of ABC's Jimmy Kimmel Live.上句中的had never heard of是虚拟语气吗，表达怎样的含义？谢谢老师的回答。