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: Energy do ecosystems absorb on the earth.

Answer: What do ecosystems absorb on the earth?


Question: A wall of rocks or concrete a called a groin.

Answer: What is a wall of rocks or concrete called?


Question: In harmonic motion there is always restorative force force, which acts in the opposite direction of the velocity.

Answer:
In harmonic motion there is always what force, which acts in the opposite direction of the velocity?