twoplane theory of chiasma

例句：

1. 1. The bird's two wings are spread wide to catch the wind.
   这只鸟的翅膀展开来捕捉风。
2. 2.The two planes circled above the city, searching for a place to land.
   两架飞机在城市上空盘旋，寻找着陆点。
3. 3. The two planes were flying at different altitudes when they collided.
   两架飞机在飞行时相撞了。