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: The outer layer of the sun is made up of plasma.

Answer: What is the outer layer of the sun made up of?


Question: The opening in the front of the eye is called pupil.

Answer: What is the opening in the front of the eye called?


Question: A(n) anion is formed when an element gains one or more electrons.

Answer:
What is formed when an element gains one or more electrons?