6. In which one of the following situations would you observe signs of fermentation first? a. a flask with dried yeast only in a warm room (20 °C) b. a flask with dried yeast and water in a warm room (20 °C) c. a flask with dried yeast, water and sugar in a refrigerator (4 °C) d. a flask with dried yeast, water and sugar in a warm room (20 °C)​