The correct explanation for why only the ratio \( \frac{124}{344} \) is a fraction while the ratio \( \frac{109}{124} \) is not a part-to-whole comparison is:
A fraction should show a part-to-whole comparison.
In \( \frac{124}{344} \), 124 (the votes for Rosalia) is the part, while 344 (the total votes cast) is the whole. Therefore, this ratio represents the portion of votes that Rosalia received out of the total votes.
On the other hand \( \frac{109}{124} \) compares the votes for Jocelyn (part) to the votes for Rosalia (not the total votes, but just another candidate's votes). This is not a part-to-whole comparison since it does not compare a part to the total number of votes cast.
Thus, only \( \frac{124}{344} \) accurately describes a fraction showing a part-to-whole relationship.