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: Collision theory tells us that molecules need to collide in order for a reaction to take place. All else being equal, anything that increases the frequency of collisions would also increase the rate of reaction. One way to do this is to increase the concentrations of one or more of the reactants. Using a real world example, a busy freeway will experience much more frequent car collisions than a fairly empty neighborhood street. Similarly, forcing more randomly moving molecules into the same amount of space will cause an increased number of collisions over a given length of time, providing the reactants with more opportunities to transform into products. 
Story: John is a chemical engineer with a pharmaceutical company. He is trying to develop a drug that can be absorbed by the system in different rates. To that end, he conducted two experiments. In one case, he used lower concentrations of reactants, he called it case A. Then he used the same reactants in a higher concentration. He called it case B. 
Question: In case case B, would the frequency of collisions be higher or lower than in case A?
answer:
higher.


question:
Background Paragraph: Before iodized salt was developed, some people experienced a number of developmental difficulties, including problems with thyroid gland function and mental retardation. In the 1920s, we learned that these conditions could usually be treated easily with the addition of iodide anion to the diet. One easy way to increase iodide intake was to add the anion to table salt. This simple step greatly enhanced health and development. Large amounts of iodide ion are also found in seaweed such as kelp (see picture above) and saltwater fish. 
Story: People from two villages ate lots of salt. People from Salt village used regular salt, while people from Sand village people used iodized salt in their diets, after talking to specialists. 
Question: Which village had fewer people experience developmental difficulties?
answer:
Sand.


question:
Background Paragraph: Ecology is the study of ecosystems. An ecosystem consists of all the living and nonliving components of the habitat. Whereas nutrients and certain elements are recycled through ecosystems, energy moves in just one direction. Many interactions among species within an ecosystem are centered around the flow of energy. The formation of ecosystems, from new land to current habitats, is usually based on the pioneer species, and these species are able to live in an area due to the nonliving factors, such as the climate, the soil and the amount of rainfall, of that area. The populations within an ecosystem also determine the stability of the system. Recent tremendous increases in the human population have raised many important ecological issues. 
Story: Two brothers liked natural sciences. Ben decided to study Ecology, while his brother Dan decided to study Geography. They studied a lot and became very good at these subjects. 
Question: Which brother studied fewer living components of the habitat?
answer:

Dan.