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

Input: Consider Input: All cells have the small size in common.

Output: What do all cells have in common?

Input: Consider Input: Renewable energy sources emit fewer or no greenhouse gases.

Output: What type energy sources emit fewer or no greenhouse gases?

Input: Consider Input: Amines are classified according to the number of carbon atoms bonded directly to a(n) nitrogen atom.
Output: Amines are classified according to the number of carbon atoms bonded directly to what atom?