A biоlоgy student suspects thаt yeаst will ferment mоnosаccharides faster than disaccharides. He performs a controlled experiment to explore this hypothesis. He tests the following experimental hypothesis: HE: Under identical growth conditions, the yeast Saccharomyces cerevisiae will produce CO2 at a higher rate with a monosaccharide than a disaccharide. What is the independent variable in this experiment? Group of answer choices