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.

Background Paragraph: Boys and girls between the ages of 9 and 13 should get 9 mg of iron every day. Girls between the ages of 14 and 18 should get 15 mg of iron every day. Boys between the ages of 14 and 18 should get 11 mg of iron every day. Pregnant women need the most iron—27 mg daily. Good sources of iron include shellfish, such as clams and oysters. Red meats, such as beef, are also a good source of iron. Non-animal sources of iron include seeds, nuts, and legumes. Breakfast cereals often have iron added to them in a process called fortification. Some good sources of iron are listed below ( Table below ). Eating vitamin C along with iron-containing food increases the amount of iron that the body can absorb. 
Story: David works as a nutritionist with the public health department. He categorized the certain sections of his county's population. First he categorized boys and girls between nine and thirteen years as cat A. Then he put girls between fourteen and eighteen years in cat B, and boys of the same age in cat C. Lastly, he categorized pregnant women as cat D. He needs to recommend healthy diet, especially iron intake, for each group. 
Question: Would cat B need less or more iron than cat A?
more.

Background Paragraph: Chemists look at the world in two ways, often simultaneously. The two worlds of the chemist are the macroscopic world and the microscopic world. Macroscopic refers to substances and objects that can be seen, touched, and measured directly. Microscopic refers to the small particles that make up all matter. Chemists must observe matter and do experiments macroscopically and then make generalizations and propose explanations that are microscopic in nature. For example, anyone can observe the physical change in appearance that occurs as an iron object such as a tractor that is left out in the elements gradually turns to rust. However, a chemist looks at the rusting tractor and thinks about what is going on with the individual atoms that make up the iron and how they are changing as a result of exposure to oxygen in the air and water from rain. Throughout your study of chemistry, you will often switch back and forth between the macroscopic and microscopic worlds. 
Story: Two cousins went to college to get a B.S. Greg studied Biology, and his younger cousin Dawn decided to study chemistry. They both graduated Summa Cum Laudae. 
Question: Which cousin studied less about the way chemists look at the world?
Greg.

Background Paragraph: Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. 
Story: Two students from the same class, studies different types of animals. Bill studied predators, while John studied grazers. 
Question: Which student didn't find out that predators can be keystone species?

John.