instruction:
In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.
question:
Question: Expansion of a gas into a vacuum is irreversible because the external pressure is measurably less than the internal pressure of the gas, and no states of what exist? Answer: equilibrium
answer:
Expansion of a gas into a vacuum is irreversible because the external pressure is measurably less than the internal pressure of the gas, and no states of equilibrium exist.

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Question: What is the hollow and muscular balloon-shaped organ that collects urine? Answer: urinary bladder
answer:
The urinary bladder is the hollow and muscular balloon-shaped organ that collects urine.

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Question: Photoautotrophs and chemoautotrophs are two basic types of what? Answer: autotrophs
answer:
Photoautotrophs and chemoautotrophs are two basic types of autotrophs.