Why If-function is used in spreadsheet?

The correct answer is option 1- To implement different action corresponding to different conditions.

Excel has a rich library of various built-in functions including financial functions, which can be directly used to carry out various (otherwise complex) calculations. A formula may use one or more such functions. In applications of excel, some of the formulae use absolute address. The absolute address is used for those cells whose content should not change while the formula containing such cells is copied to other cells. If-function is also used in these applications. If-function is used to implement different action corresponding to different conditions.