formation

飞机以编队飞行在头顶。

The planes flew overhead in ___formation.

这个洞穴里有我所见过的最不可思议的冰层形成。

The cave had the most incredible ice ___formation I had ever seen.

科学家们在显微镜下观察了晶体的形成。

Scientists observed the ___formation of a crystal under the microscope.