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.

[Q]: Question: What type of substance is any matter that has a fixed chemical composition and characteristic properties? Answer: pure chemical substance
[A]: Pure chemical substance type of substance is any matter that has a fixed chemical composition and characteristic properties.


[Q]: Question: What kind of system do echinoderms possess? Answer: water-based circulatory
[A]: Echinoderms possess a water-based circulatory system.


[Q]: Question: How does a cell's membrane keep extracellular materials from mixing with it's internal components? Answer: provides a barrier
[A]:
A cell's membrane provides a barrier to keep extracellular materials from mixing with its internal components.