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

Input: Consider Input: Saturated hydrocarbons hydrocarbons contain only single bonds between carbon atoms.

Output: What hydrocarbons contain only single bonds between carbon atoms?

Input: Consider Input: Fires, mainly caused by lightning, are a natural disturbance in temperate grasslands.

Output: Fires, mainly caused by what, are a natural disturbance in temperate grasslands?

Input: Consider Input: The stratosphere is the layer above the troposphere.
Output: What is the layer above the troposphere?