Given a scientific passage and an answer, generate a question for the given answer.
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Question: Passage: Figure 14.3 The Tongue The tongue is covered with small bumps, called papillae, which contain taste buds that are sensitive to chemicals in ingested food or drink. Different types of papillae are found in different regions of the tongue. The taste buds contain specialized gustatory receptor cells that respond to chemical stimuli dissolved in the saliva. These receptor cells activate sensory neurons that are part of the facial and glossopharyngeal nerves. LM 1600. (Micrograph provided by the Regents of University of Michigan Medical School ©️ 2012). Answer: papillae

Answer: What is the name of the small bumps that contain taste buds and covers the tongue?

Question: Passage: Density is defined as the mass of an object divided by its volume. Propose a unit of density in terms of the fundamental SI units. Answer: volume

Answer: Density is defined as the mass of an object divided by its what?

Question: Passage: Brewers of beer and wine use yeast to add alcohol to beverages. Traditional varieties of yeast not only make but also limit the quantity of alcohol in these beverages, because above 18% by volume, alcohol becomes toxic to the yeast itself. Wine is produced by fermentation of the natural sugars present in grapes and other kinds of fruit. Beer, whiskey, and vodka are produced by fermentation of grain starches that have been converted to sugar by the enzyme amylase, and rum is produced by fermentation of sugarcane. In each of these fermentations, sugars are converted into small amounts of ATP, using and regenerating NAD + in the process, and producing ethanol and carbon dioxide. Scientists have recently developed new strains of yeast which can tolerate up to 25% alcohol by volume. These are used primarily in the production of ethanol fuel. Answer: to make alcohol

Answer:
Why do beer brewers add yeast to the wort?