Concept:Fermentation:Fermentation is an anaerobic process where oxygen is absent, and energy can be released from glucose.It occurs in yeast cells, bacteria, and the muscles of animals.It is an anaerobic pathway in which glucose is broken down.Louis Pasteur discovered the fermentation process.Alcoholic fermentation is the process of using yeast to convert sugar into alcohol.Some examples of fermentation are bread, yogurt, alcoholic beverages, etc.Explanation:Yeast:Yeast is a unicellular fungus and a microbe.It lives as a saprophyte on starch and sugar-rich substances such as in date palm, molasses, or grapes.Saccharomyces cerevisiae, the yeast used for bread making and is commonly known as brewers yeast.It is used for fermenting malted cereals and fruit juices to produce ethanol.When yeast is put into bread dough it eats the sugar and digests it and gives off alcohol and CO2 gas.So, during bread baking, the sweet aroma is produced because sugar is converted to alcohol and CO2 which causes bread to rise.The chemical formula for alcoholic fermentation: C6H1206 ? 2C2H5OH + 2CO2Thus from the above discussion, it is clear that the correct answer is sugar is converted to alcohol by yeast through the process of fermentation.