The correct answer is C. A group of cells.
A worksheet range is a group of cells in a spreadsheet that are selected together. Ranges can be used to perform operations on multiple cells at once, such as adding them together or formatting them in a specific way.
Option A is incorrect because a command is a set of instructions that tells a computer to perform a specific task. Option B is incorrect because a range of values is a set of numbers that are separated by commas. Option D is incorrect because a group of worksheets is a collection of multiple spreadsheets that are stored together in a workbook.