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

A diet rich in calcium and vitamin d may reduce the risk of osteoporosis and related bone fractures.
A diet rich in calcium and what vitamin may reduce the risk of osteoporosis and related bone fractures?

The main advantage of urea is its very low toxicity.
The main advantage of urea is its very low what?

A human cannot survive the loss of the liver of the following.

A human CANNOT survive the loss of which of the following?