You are given a background paragraph that describes one or more causal or qualitative relationships such as a relationship in economics or a scientific law and a story that makes use of the concepts or the relationship described in the provided paragraph. You are also given a question about the story that requires an understanding of the relationship described in the background paragraph and the story. You need to come up with an answer to the given question; the answer will be a span from either the question or the story. In order to correctly answer the given question, you need to understand the relationship mentioned in the background paragraph and should be able to use it to understand that in the story. Your answer can not consist of any word that is not mentioned in any of these: the background paragraph, the story, or the question. You can directly copy and paste a span from the story or the question while answering the given question.

Example Input: Background Paragraph: Baker's yeast is the common name for the strains of yeast commonly used in baking bread and bakery products, serving as a leavening agent which causes the bread to rise (expand and become lighter and softer) by converting the fermentable sugars present in the dough into carbon dioxide and ethanol. Baker's yeast is of the species Saccharomyces cerevisiae,[1] and is the same species (but a different strain) as the kind commonly used in alcoholic fermentation, which is called brewer's yeast.[2] Baker's yeast is also a single-cell microorganism found on and around the human body. 
Story: Ken is a microbiologist. He got two samples of yeasts, yeast A and yeast B, from two different businesses. Yeast A is used in a bakery, and yeast B is used in a brewery. He has to decide the characteristics of each 
yeast sample for further study.
Interestingly, despite all his curiosity, Ken doesn't like any yeast to be around him. 
Question: If Ken wants a dough sample to expand, which yeast should he use, yeast A or yeast B?
Example Output: yeast A.

Example Input: Background Paragraph: Hemophilia is the name of a group of hereditary diseases that affect the body's ability to control blood clotting. Hemophilia is caused by a lack of clotting factors in the blood. Clotting factors are normally released by platelets. Since people with hemophilia cannot produce clots, any cut can put a person at risk of bleeding to death. The risk of internal bleeding is also increased in hemophilia, especially into muscles and joints. This disease affected the royal families of Europe. 
Story: Two brothers took a blood test. The doctor found out that Tim had hemophilia, while his brother Rick had normal blood cells and was healthy. 
Question: Which brother had a lower risk of bleeding to death?
Example Output: Rick.

Example Input: Background Paragraph: Curds are a dairy product obtained by coagulating milk in a process called curdling. The coagulation can be caused by adding rennet or any edible acidic substance such as lemon juice or vinegar, and then allowing it to coagulate. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria) will also naturally produce curds, and sour milk cheeses are produced this way. Producing cheese curds is one of the first steps in cheesemaking; the curds are pressed and drained to varying amounts for different styles of cheese and different secondary agents (molds for blue cheeses, etc.) are introduced before the desired aging finishes the cheese. The remaining liquid, which contains only whey proteins, is the whey. In cow's milk, 90 percent of the proteins are caseins. 
Story: Dan likes to experiment with different food items. Today, he wants to make curds out of milk and see how it differs from plain milk. For his experiment he collected three bottles of milk, bottle A, bottle B, and bottle C. Bottle A and bottle B milk are pasteurized, but bottle C milk is just raw milk. He kept the bottle A milk intact, but made curd out of bottle B and bottle C milk. 
Question: In which milk casein would not tangle into solid masses, bottle A or bottle B?
Example Output:
bottle A.