Explanation:

- The original sentence contains a grammatical error: "whether its accurateness." This phrase is awkward and incorrect due to the use of "accurateness" instead of "accuracy."

- Option 1: "about they are accurate" is ungrammatical. "They" is used incorrectly as the subject, and it confuses the structure of the sentence.

- Option 2: "whether how they were accurate" is redundant and unclear. Using both "whether" and "how" together creates a logical inconsistency.

- Option 3: "about their accuracy" is clear and correct. It replaces the awkward phrase with a grammatically correct expression.

- Option 4: "No substitution required" would be incorrect due to the issue noted.

The correct substitution for the underlined segment is:

- Option 3: about their accuracy