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

Q: Cells are small biological structures that make up all living things, including the human body.

A: What small biological structures make up all living things, including the human body?
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Q: Tight junction is the term for a watertight seal between two adjacent animal cells.

A: What is the term for a watertight seal between two adjacent animal cells?
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Q: Frequency of a electromagnetic wave can be calculated using the wave equation due to their speed always being constant.

A:
What of a electromagnetic wave can be calculated using the wave equation due to their speed always being constant?
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