Answer: 2. A version older than Excel 2016 was used to create the workbook .
Explanation: The compatibility mode appears whenever a workbook initially prepared using an excel software version which is older than the excel software which is used in opening the file or workbook. The compatibility mode is displayed due to the difference in software version where the original version used in preparing the workbook is older than the version used in opening the workbook. With compatibility mode displayed, new features won't be applied on the document.