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

Input: Consider Input: The main advantage of urea is its very low toxicity.

Output: The main advantage of urea is its very low what?


Input: Consider Input: Age causes reduction of elasticity in all organs.

Output: What causes reduction of elasticity in all organs?


Input: Consider Input: Proteins are categorized according to shape and solubility property, which correlates with it.


Output: Proteins are categorized according to shape and what property, which correlates with it?