instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Solids are categorized by the forces holding the individual atoms, ions, or molecules together.
answer:
What is categorized by the forces holding the individual atoms, ions, or molecules together?


question:
The active transport of ions across the membrane causes an electrical gradient to build up across the plasma membrane.
answer:
The active transport of ions across the membrane causes an electrical gradient to build up across the what?


question:
Foresters commonly inoculate pine seedlings with a type of fungi to promote growth.
answer:

Foresters commonly inoculate pine seedlings with a type of what to promote growth?