Given a scientific passage and an answer, generate a question for the given answer.

Q: Passage: Figure 12.7 Statues made from carbonate compounds such as limestone and marble typically weather slowly over time due to the actions of water, and thermal expansion and contraction. However, pollutants like sulfur dioxide can accelerate weathering. As the concentration of air pollutants increases, deterioration of limestone occurs more rapidly. (credit: James P Fisher III). Answer: air pollutants

A: Deterioration of limestone occurs more rapidly as the concentration of what increases?
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Q: Passage: When there is no mass in a volume of space, the space is not curved. An object passing through such space would follow a straight line in our normal way of thinking of a straight line. Answer: curved

A: When there is no mass in a volume of space, the space is not what?
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Q: Passage: Opposite charges attract and like charges repulse. Answer: repulse

A:
Opposite charges attract and like charges do what?
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