What does it mean when #div/o! is displayed and a green triangle is added to the upper-left corner of the cell? a. the formula doesn't start with a= sign b. the formula can be calculated but there is an error c. the formula cannot be caculated because there is an error d. the error checking feature is disabled

This is most usually caused by the formula dividing by 0 or getting an undefined result, for example, if a cell used in the formula has text instead of a number. There is no result that can be calculated using the formula, so the answer should be C.

If you don't start the formula with an = sign, you will get the text of the formula rather than any numerical result. If the formula could be calculated, the cell would give an actual number.