Given a scientific question, generate a correct answer to it.

Q: What "kind" of water may take longer to become contaminated than surface water, while the natural cleaning process may take longer?

A: groundwater
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Q: What does the moon not have to protect it from extreme temperatures?

A: atmosphere
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Q: In atherosclerosis, thickening of an arterial wall due to this can restrict blood flow through the artery?

A:
plaque formation
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