Which one among equal sign, comma, ampersand, colon cannot be used in an Excel spreadsheet formula?

The correct answer is &. Ampersand is a logogram. It represents the conjunction & and originated from the Latin word et, which stands for and. It's history dates back to the Old Roman Cursive of 1st Century AD. It is commonly used in business names and film credits.

The ampersand is unable to be used in Excel because it is a command code. This command is used to join two or more text strings or words together. However, there is a word around. To use & in Excel, put two ampersands together with no space. By doing so, Excel will display one.