We recently conducted a series of science lessons on micro-organisms. The last one included investigating the reaction of yeast when mixed with other ingredients. The formal part of the investigation was ensuring the test was a fair one with consistent measurements, and that we included a number of options and a control. We found that the yeast really enjoyed water, energy (sugar) and warmth (the water was heated). Water and yeast alone had no reaction, neither did water and sugar, or sugar and water. You can see the results in the photo below. Can you tell which one shows the reaction?