Explanation:

Let's evaluate the sentence and options:

- Original Sentence: Practically (every part) of the papaya tree is used by man.

1. either part: Implies a choice between two, which doesn't fit here since multiple parts are used.

2. each one: Suggests focusing on individual parts, but doesn't quite capture the collective usage intended.

3. every one: Similar to "each one," which reads slightly better but doesn't improve clarity.

4. No improvement: The original phrase clearly conveys that all parts of the tree are used.

- Correct Answer: No improvement. This phrase expresses the intended meaning perfectly.

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