In 2015 , Richard Branson offered Stephen Hawking a seat on the Virgin Galactic spaceship for free .
In 2015 , Richard Branson offered Stephen Hawking a seat free of charge on the Virgin Galactic spaceship .
In 2015 , Richard Branson offered Stephen Hawking a seat free of charge on the Virgin Galactic spaceship .
解释一下这段文字: In 2015 , Richard Branson offered Stephen Hawking a seat on the Virgin Galactic spaceship for free . 输出: