Alcohols are important industrial solvents. Ethanol, methanol, propanol and butanol are produced commercially by fermentation activity of some fungi, majorly yeasts. During fermentation, yeast cells convert cereal derived sugars into ethanol and `CO_2`. At the same time hundreds of secondary metabolites that influence the aroma and taste of alcohol are produced. Sugar concentration affects the rate of fermentation reactions. Yeast cannot grow in very strong sugar solution. The rate of alcohol production is measured on the basis of

Options

A. amount of sugar present in the medium
B. amount of `CO_2` produced per unit time
C. amount of yeast added in the medium
D. all of these

Answer

B