instruction:
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.
question:
Background Paragraph: Some individuals have a specific mutation in the primary sequence of their hemoglobin molecules that causes them to aggregate, resulting in a deformation of their red blood cells. This abnormality is genetic in nature. A person may inherit the gene from one parent and have sickle cell trait (only some of the hemoglobin is hemoglobin S), which is usually not life-threatening. Inheriting the gene from both parents will result in sickle cell disease, which is a very serious condition. 
Story: Doctors studied two groups of patients. Group W which had people with sickle cell disease, and group A which had normal people in it. 
Question: Which group had fewer individuals inheriting the gene from both parents ?
answer:
group A.


question:
Background Paragraph: In nature, when the population size is small, there is usually plenty of food and other resources for each individual. When there is plenty of food and other resources, organisms can easily reproduce, so the birth rate is high. As the population increases, the food supply, or the supply of another necessary resource, may decrease. When necessary resources, such as food, decrease, some individuals will die. Overall, the population cannot reproduce at the same rate, so the birth rates drop. This will cause the population growth rate to decrease. 
Story: Bill studied two herds of deer for a year. He was in love with nature. He observed the large herd named Alpha inhabited an area with fewer resources. Herd Beta was a smaller one, and they grazed on an abundance of plants. 
Question: Which herd had more food available for each individual?
answer:
Beta.


question:
Background Paragraph: In the U.S., the majority of electricity is produced by burning coal or other fossil fuels. This causes air pollution, acid rain, and global warming. Fossil fuels are also limited and may eventually run out. Like fossil fuels, radioactive elements are limited. In fact, they are relatively rare, so they could run out sooner rather than later. On the other hand, nuclear fission does not release air pollution or cause the other environmental problems associated with burning fossil fuels. This is the major advantage of using nuclear fission as a source of energy. 
Story: Us and Canada are two friendly countries. Canada uses alternative methods to produce electricity while the US use more coal and oil. Both countries recently participated in a Global Warming Council. 
Question: Which country causes more air pollution?
answer:

US.