不久他又独自一人乘氢气球上升到3000米高空，作了一次35分钟的单独飞行。

Soon he alone rose to the ball of hydrogen by 3000 meters high, made a separate 35-minute flight.

youdao

不久他又独自一人乘氢气球上升到3000米高空，作了一次35分钟的单独飞行。

Soon he alone rose to the ball of hydrogen by 3000 meters high, made a separate 35-minute flight.

youdao