instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
People stopped adding lead to gasoline because of environmental pollution.
answer:
Why did people stop adding lead to gasoline?


question:
Although they differ vastly in hardness, pencil lead and diamonds both contain carbon.
answer:
Although they differ vastly in hardness, pencil lead and diamonds both contain what element?


question:
Endoscopes are used to explore the body through various orifices or minor incisions.
answer:

Endoscopes are used to explore the body through various orifices or these?