Necessary.

Phenomenon, purpose, pleasure, exceptionally, wealthy, uniqueness, awesome, astronauts, weightlessness, advantage, success, access, aspira­tion, subsidiary, crew, scientific, whilst, resume, venture, charge, main­tenance, decision, entrepreneur, concerns, vehicle, adventure, viewed, suborbital, altitude, twinkle, law, soil, license, circumlunar, scenario, announce, supersede interstellar, future, create, discard, fuel, beyond, feasibility, tycoon, acquire, design, billionaire.

Unit 2. Space Tourism

 

2. Compare and mind the difference:

 

BrE

AmE

to symbolise kilometre starfield

to symbolize kilometer star field