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

Q: Although they differ vastly in hardness, pencil lead and diamonds both contain carbon.

A: Although they differ vastly in hardness, pencil lead and diamonds both contain what element?
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Q: You call materials able to conduct electricity with 100% efficiency, meaning that no energy is lost during the electrical transmission, superconductors.

A: What do you call materials able to conduct electricity with 100% efficiency, meaning that no energy is lost during the electrical transmission?
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Q: The ph scale measures acids and bases and has 7 as a neutral value.

A:
Which scale measures acids and bases and has 7 as a neutral value?
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