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

Example Input: Temperature and sky conditions are both used to describe weather.
Example Output: Which two observations are both used to describe weather?

Example Input: Phospholipids are the main component of the cell membrane.
Example Output: What is the main makeup of the cell membrane?

Example Input: Solar and wind are still expensive compared to fossil fuels.
Example Output:
Solar and wind are still expensive compared to what?