Is there anything before that? Like any info of the total students?
Relative frequency is basically, the percentage of a data set that liked this one thing.
In this case, say that there was 200 students. Then the relative frequency would be 115/200, or 0.575, or 57.5%.
[Edit: There are 950 ish students, according to the graph you posted, and based on what I said above, 115/950 is about 0.12, or C.]
