The correct option is
D Barley
Beer is produced from malted barley. It has an alcohol content of about 3-6%. The formation of beer is carried out with the help of brewer's yeast Saccharomyces cerevisiae. The yeast causes fermentation of malted barley (the germinating grains of Barley that have been dried). This results in the formation of ethyl alcohol along with carbon dioxide. It also provides characteristic taste and flavour to beer.
So, the correct answer is 'Barley'.