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

Ex Input:
Passage: Photosynthetic organisms include plants, algae, and some bacteria. Answer: photosynthetic

Ex Output:
Plants, algae and bacteria are all examples of what type of organism?

Ex Input:
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

Ex Output:
Deterioration of limestone occurs more rapidly as the concentration of what increases?

Ex Input:
Passage: The menstrual cycle is a series of changes in the reproductive system of mature females that repeats every month on average. It includes changes in the uterus as well as development of an egg and ovulation. If fertilization does not occur, menstruation occurs and the cycle repeats. Answer: lack of fertilization

Ex Output:
What causes the menstrual cycle to be repeated?