The empirical formula gives the relative ratio of atoms in each element. Therefore, it simplifies the whole numbers. For example C2H6 can be reduced to CH3 because they share the greatest common factor (2). The answer to this question would be #1. C4H10 can be reduced to C2H5 because 4 and 10 are both divisible by 2. C2H5 can not be reduced any further. All of the other options do not have a greatest common factor making them a empirical formula.
