Luyện ngữ pháp - Destination C1 and C2 - (Unit 7: Grammar - Passives and causatives)


Write one word in each gap.

The scramjet

Imagine (1) transported around the globe in a matter of hours, rather than the 24 hours which (2) currently required to get from London to Sydney. Such is the promise of the scramjet, a highly experimental type of engine which has been (3) development over the past couple of decades. In a conventional jet engine, air (4) sucked into the engine at speeds below the speed of sound, where it is mixed (5) fuel, ignited, and the exhaust gases provide thrust. In a scramjet, which has to (6) taken to supersonic speeds by conventional means before it will operate, the air enters at supersonic speeds.

It has (7) estimated that a scramjet might be capable of travelling at 12-24 times the speed of sound. However, the technology (8) been found to be extremely difficult to control. Although scientists (9) had scramjets perform short flights, commercial aircraft are still a long way in the future, and indeed may never (10) successfully developed.



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