In a spreadsheet program, what cell is directly below cell AB4?

The cell directly below AB4 is AB5. In a spreadsheet, cells are referenced using a column letter followed by a row number. The letter indicates the column, and the number indicates the row.

AB4 is located in column AB and row 4, so to find the cell directly below it, you simply increase the row number by one while keeping the column constant. Thus, the cell directly below AB4 is AB (the same column) and 5 (the next row).

This understanding of how spreadsheet cell references work is essential for anyone working with data in programs like Microsoft Excel or Google Sheets. The other choices involve either different columns (AC or BC) or different row numbers which do not align directly with AB4, making them incorrect.