Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Ex Input:
Some gametophytes develop underground and form mycorrhizal associations with fungi.

Ex Output:
Some gametophytes develop underground and form mycorrhizal associations with what?

Ex Input:
The ability of matter to combine chemically with other substances is known as reactivity.

Ex Output:
The ability of matter to combine chemically with other substances is known as?

Ex Input:
Planes fly in stratosphere layer of the atmosphere because there is less friction and turbulence.

Ex Output:
Planes fly in what layer of the atmosphere because there is less friction and turbulence?