Which examples use parentheses and brackets correctly?

The use of parentheses and brackets in the chosen example reflects proper punctuation conventions effectively. Parentheses are employed in the sentence to provide supplementary information that is not essential to the main statement. This creates clarity by offering additional context about the time of the meeting ("it's at 9:00 a.m.") without interrupting the flow of the main clause, allowing the reader to still understand the primary message even if they choose to disregard the parenthetical information.

Using parentheses in this way enhances readability and keeps the reader's attention on the main point while still providing valuable details. The other options do incorporate brackets and parentheses, but they may not align as closely with conventional usage or clarity. The effective combination of parentheses in the selected sentence exemplifies correct and purposeful punctuation.