page 06 7. In an investigation into fermentation, yeast was grown in a flask of glucose solution for 20 hours at 20 °C. The graph shows the concentrations of ethanol and glucose in the flask over the period of the investigation. Ethanol concentration (grams per litre) Glucose concentration (grams per litre) Time (hours) 0 5 10 15 20 0 1 2 3 4 0 2 4 6 8 What was the glucose concentration when the ethanol concentration was 3·3 grams per litre? A 1·2 grams per litre B 2·2 grams per litre C 2·4 grams per litre D 6·6 grams per litre