Answer:
The correct empirical formula, if the ratio is 1:1:3, is: FeS3
Step-by-step explanation:
In this case, the empirical formula indicates the simplest whole-number ratio of atoms present in a compound. The ratio 1:1:3 means that for every 1 atom of the first element, there is 1 atom of the second element and 3 atoms of the third element. Among the options provided, FeS3 is the only one that fits this ratio.