Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: Cloud types include cirrus, stratus, and cumulus. Answer: clouds

Ex Output:
Cirrus, stratus, and cumulus are types of what?

Ex Input:
Passage: The cornea is the transparent outer covering of the eye. It protects the eye and also acts as a convex lens, helping to focus light that enters the eye. Answer: cornea

Ex Output:
What is the transparent outer covering of the eye?

Ex Input:
Passage: Opening Essay Although yeast has been used for thousands of years, its true nature has been known only for the last two centuries. Yeasts are single-celled fungi. About 1,000 species are recognized, but the most common species is Saccharomyces cerevisiae, which is used in bread making. Other species are used for the fermentation of alcoholic beverages. Some species can cause infections in humans. Yeasts live primarily on sugars, such as glucose (C6H12O6). They convert glucose into carbon dioxide (CO2) and ethanol (C2H5OH) in a chemical transformation that is represented as follows:. Answer: bread making

Ex Output:
Yeasts are single-celled fungi. about 1,000 species are recognized, but the most common species is saccharomyces cerevisiae, which is used in this?