Which term refers to cells that cannot be modified or adjusted?

The correct term for cells that cannot be modified or adjusted is "Read-only cells." These types of cells are typically locked to prevent any changes, preserving the integrity of the data they contain. This feature is especially useful in planning and reporting scenarios where certain values are finalized, such as historical data or results directly pulled from a secure source. By ensuring that these cells remain unchanged, organizations can maintain accurate reports and analyses without the risk of accidental alterations.

The other choices represent different concepts. Rollup cells are often used to summarize data from child cells into a parent cell, allowing for a consolidated view of information. Sheet notes provide additional context or comments regarding certain data but do not prevent modifications to the data itself. Notes character limits refer to restrictions on how much text can be entered in a note, which is unrelated to the concept of cell modifications.