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: Active immunity can also result from immunization. Immunization is the deliberate exposure of a person to a pathogen in order to provoke an immune response and the formation of memory cells specific to that pathogen. The pathogen is often injected. However, only part of a pathogen, a weakened form of the pathogen, or a dead pathogen is typically used. This causes an immune response without making the immunized person sick. This is how you most likely became immune to measles, mumps, and chicken pox. 
Story: When Emily was 4 years old she came down with a case of the chicken pox. She is now 14 and her younger brother Victor has now caught the chicken pox from another child at school. Emily opts to stay home and take care of him. 
Question: Given Emily never had the chicken pox, will Emily now have an increased or decreased chance of getting chicken pox from her brother?
increased.

Background Paragraph: The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. These distinctions form the basis for the division of rivers into upland and lowland rivers. The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a canopy derive the majority of their food base from algae. Anadromous fish are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species. A dam produces negative effects that continue down the watershed. The most important negative effects are the reduction of spring flooding, which damages wetlands, and the retention of sediment, which leads to loss of deltaic wetlands. 
Story: Jill lives out in a peaceful quiet area with hardly any other people around. Next to her home is a calm peaceful river. The river doesn't have an official name that she is aware of, but her family has always called it River Treetop due to the large tree next to it. Also next to her house, there is a roaring river that runs for miles. The river is so loud that it can be hard to hear yourself think sometimes if you are sitting next to it. For this reason, Jill has always referred to the river as River Chaos. 
Question: Is the biodiversity in River Treetop higher or lower than in River Chaos?
lower.

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: Which group would need more iron, cat B or cat C?

cat B.