Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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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: Opaque is the term for matter that does not let any light pass through.

Answer: What is the term for matter that does not let any light pass through?


Question: Esophagus, stomach, intestines are the structures that make up the digestive system in the human body.

Answer:
Which example best shows structures that make up the digestive system in the human body?