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

Q: Passage: Plants in the haploid generation are called gametophytes . They form from haploid spores. They have male and/or female reproductive organs and reproduce sexually. They produce haploid gametes by mitosis. Fertilization of gametes produces diploid zygotes. Zygotes develop into the diploid generation. Answer: through mitosis

A: How do gametophyte plants form haploid gametes?
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Q: Passage: To this point, we have examined the relationships between any two of the variables of , , and , while the third variable is held constant. However, situations arise where all three variables change. The combined gas law expresses the relationship between the pressure, volume, and absolute temperature of a fixed amount of gas. For a combined gas law problem, only the amount of gas is held constant. Answer: pressure

A: The combined gas law involves three properties of a gas - volume, absolute temperature, and what?
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Q: Passage: The saguaro cactus pictured in Figure below has adapted in all three ways. When it was still a very small plant, just a few inches high, its shallow roots already reached out as much as 2 meters (7 feet) from the base of the stem. By now, its root system is much more widespread. It allows the cactus to gather as much moisture as possible from rare rainfalls. The saguaro doesn't have any leaves to lose water by transpiration. It also has a large, barrel-shaped stem that can store a lot of water. Thorns protect the stem from thirsty animals that might try to get at the water inside. Answer: transpiration

A:
The saguaro doesn't have any leaves to lose water by which process?
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