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

[EX 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
[EX A]: The combined gas law involves three properties of a gas - volume, absolute temperature, and what?

[EX Q]: Passage: 41.4 Nitrogenous Wastes Ammonia is the waste produced by metabolism of nitrogen-containing compounds like proteins and nucleic acids. While aquatic animals can easily excrete ammonia into their watery surroundings, terrestrial animals have evolved special mechanisms to eliminate the toxic ammonia from their systems. Urea is the major byproduct of ammonia metabolism in vertebrate animals. Uric acid is the major byproduct of ammonia metabolism in birds, terrestrial arthropods, and reptiles. Answer: urea
[EX A]: When vertebrate animals metabolize ammonia what is the primary byproduct that is produced?

[EX Q]: Passage: Gamma emission is the release of energy in the form of high energy electromagnetic waves. Answer: gamma emission
[EX A]:
What is the release of energy in the form of high energy electromagnetic waves?