The engines would have variable nozzles, which would be fully opened on take-off and landing, so that the exhaust would be slow and relatively quiet, and narrowed when the aircraft was cruising, providing the necessary speed.
【核心詞彙】
variable a.易變的，多變的
exhaust n.排氣，廢氣，排氣管
relatively ad.相當地，相對地 take-off起飛
【結構分析】
本句主句爲The engines would have variable nozzles。其後的定語從句比較複雜，以逗號後and爲切入點，得到which would be fully narrowed...，關係代詞which指代先行詞nozzles在從句中作主語。其中so that引導的結果狀語從句so that the exhaust would be slow and relatively quiet說明(nozzles)would be fully opened on take-off and landing情況發生時所產生的.結果，句末的現在分詞結構providing the necessary speed作(nozzles)would be narrowed when the aircraft was cruising情況發生時的伴隨結果，其中when引導的從句作時間狀語。
【參考譯文】
引擎將配有各種各樣的尾噴管，在起飛和降落時這些尾噴管會全部開啟，這樣噴氣速度會下降，噪音也會更小;而在飛機巡航過程中，尾噴管將變小以保證必要的飛行速度。