In order to determine which type of sugar showed the greatest rate of fermentation, you would need to refer to the graph created by the students. Typically, the sugar that reaches the highest level of fermentation product (such as carbon dioxide or alcohol) over a given time would be considered to have the greatest rate of fermentation.
Without the visual data, I can't specify which sugar had the greatest rate. If you can describe the trends or key data points from the graph, I would be happy to help you analyze it!