This would solve the problem of ventilation.ventilation为什么不加the?

题目

This would solve the problem of ventilation.ventilation为什么不加the?
还有 the British had not feared invasion.invasion为什么不加the?
下面是全文
In 1858,a French engineer,Aime Thome de Gamond,arrived in England with a plan for a twenty-one-mile tunnel under the English Channel.He said that it would be possible to build a platform in the centre of the Channel.This platform would serve as a port and a railway station.The tunnel would be well-ventilated if tall chimneys were built above sea level.In 1860,a better plan was put forward by an Englishman,William Low.He suggested that a double railway-tunnel should be built.This would solve the problem of ventilation,for if a train entered this tunnel,it would draw in fresh air behind it.Forty-two years later a tunnel was actually begun.If,at the time,the British had not feared invasion,it would have been completed.The world had to wait almost another 100 years for the Channel Tunnel.It was officially opened on March 7,1994,finally connecting Brita

答案

很简单啊 invasion是入侵的意思,这个词在文中是泛指,并没有指哪次具体的入侵,当然不加the,如果加the,那就是特指了