I do not know whether you realize it, but this condition is essential to us.
我不知道你是否了解,但是,这个条件对我们是必要的。
In 1929, three years after his flight over the North Pole, the American explorer, R.E.Byrd, successfully flew over the South Pole for the first time.
美国探险家 R。伯德在飞越北极3年之后,于1929年第一次飞越了南极。