Explanation:

- Sterile: Lacking the ability to produce or support growth; often used to describe something that is free from living microorganisms or completely clean.

- Option 1, Pure: Means not mixed with anything else, uncontaminated. While cleanliness is a shared idea, "sterile" implies complete cleanliness often without productivity.

- Option 2, Productive: Indicates the ability to produce or generate. This is almost opposite to "sterile," which suggests lack of productivity.

- Option 3, Barren: Describes something unproductive or incapable of supporting growth. It is the most similar to "sterile," emphasizing a lack of fertility or productivity.

- Option 4, Sordid: Means dirty or morally degraded. This is unrelated to the concept of "sterility."

- Correct Answer: Option 3, Barren

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