Answer:
The sentence that is grammatically correct is: Tess’ revisions to the report increased its readability significantly.
Explanation:
The fourth/last option (sentence) is correct because an apostrophe is required after the noun (Tess) to indicate that the noun (Tess) is possessive; in addition, the word "its" is appropriate, and not in a contracted form—it's—which represents "it is".
