When can a rule apply to multiple columns in a worksheet?

The correct answer indicates that a rule can apply to multiple columns in a worksheet when the formats are based on a value in another column. This is significant because conditional formatting rules often depend on the relationship between data in one column and the data in another. By referring to a specific column's value to determine the formatting for multiple other columns, it enables a more dynamic and context-sensitive approach to data visualization and analysis.

For instance, if you have a column that contains a status value (like "Complete," "Pending," or "Failed"), you can create a rule that formats other columns based on what that status indicates. This creates a coherent display that highlights relevant data across multiple columns without needing separate rules for each column's individual values.

In contrast, the other options do not capture the essence of how rules effectively apply across multiple columns. Different formatting conditions or grouping does not inherently mean the formatting rules are interlinked or share base criteria. Likewise, having identical data in all columns does not necessitate applying a single formatting rule; rather, it treats them independently unless designed to serve a collective purpose based on the reference column.