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

[Q]: Natural resource type of resource is limited in supply and cannot be replaced except over millions of years.
[A]: What type of resource is limited in supply and cannot be replaced except over millions of years?


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


[Q]: Silicon is an example of a metaloid element.
[A]:
What is an example of a metaloid element?