Answer:
A. Relative cell reference.
Step-by-step explanation:
A relative cell reference is like a pointer to a cell or range of cell in Excel. In Excel all cell references, by default, are relative cell references.
In the given instance, the cell address A4 in a formula means it is a relative cell reference. If there would have been a $ sign before A4, then it will be an absolute cell reference. But since, it is without dollar sign, it is a relative cell reference.
Therefore, option A is correct.