He joined the Royal Naval Air Service in 1915 and was posted two years later to service and rescue aircraft that crashed behind the trenches at Ypres and the Somme.是什么意思_He joined the Royal Naval Air Service in 1915 and was posted two years later to service and rescue aircraft that crashed behind the trenches at Ypres and the Somme.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句