The correct answer is CA#20.A cell reference or cell address is a combination of a column letter and a row number that identifies a cell on a worksheet.For example, A1 refers to the cell at the intersection of column A and row 1; B2 refers to the second cell in column B, and so on.A range reference is represented by the address of the upper-left cell and the lower right cell separated with a colon.There exist two address styles in Excel: A1 and R1C1.A1 is the default style used most of the time. In this style, columns are defined by letters and rows by numbers, i.e. A1 designates a cell in column A, row 1.R1C1 is the style where both rows and columns are identified by numbers, i.e. R1C1 designates a cell in row 1, column 1.There are three types of cell references in Excel:A relative reference is the one without the $ sign in the row and column coordinates, like A1 or A1:B10. By default, all cell addresses in Excel are relative.An absolute reference is the one with the dollar sign ($) in the row or column coordinates, like $A$1 or $A$1:$B$10.A mixed reference contains one relative and one absolute coordinate, like $A1 or A$1.