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: The ionization energies of the representative elements generally decrease from top to bottom within a group. This trend is explained by the increase in size of the atoms within a group. The valence electron that is being removed is further from the nucleus in the case of a larger atom. The attractive force between the valence electron and the nucleus weakens as the distance between them increases and as the shielding effect increases, resulting in a lower ionization energy for the larger atoms within a group. Although the nucl. 
Story: Rob is learning about ionization. He looks at a specific group of elements from top to bottom to figure out thier ionization energy. 
Question: Which element will have a higher shielding effect, the top element or the bottom element?
answer:
bottom element.


question:
Background Paragraph: HIV , or human immunodeficiency virus, causes AIDS. AIDS stands for "acquired immune deficiency syndrome." It is a condition that causes death and does not have a known cure. AIDS usually develops 10 to 15 years after a person is first infected with HIV. The development of AIDS can be delayed with proper medicines. The delay can be well over 20 years with the right medicines. Today, individuals who acquire HIV after 50 years of age can expect to reach an average human life span. 
Story: The police arrested two homeless people. James was 35 and had been HIV positive for 20 years, and Bill, who was 54 and was not HIV positive. They booked them and let them go. 
Question: Which person didn't have to take medicines to slow down the virus?
answer:
Bill.


question:
Background Paragraph: When humans dig up and use fossil fuels, we have an impact on the carbon cycle ( Figure below ). This carbon is not recycled until it is used by humans. The burning of fossil fuels releases more carbon dioxide into the atmosphere than is used by photosynthesis. So, there is more carbon dioxide entering the atmosphere than is coming out of it. Carbon dioxide is known as a greenhouse gas , since it lets in light energy but does not let heat escape, much like the panes of a greenhouse. The increase of greenhouse gasses in the atmosphere is contributing to a global rise in Earth’s temperature, known as global warming or global climate change. 
Story: Greg is an environmental scientist. He wants to know how earth's atmosphere differed in two different time. To that end, he selected two time periods, time A and time B. Time A is set in the year one thousand when using fossil fuels was not very common. Time B is set in the year two thousand when fossil fuels are used in large quantities. 
Question: In which time less carbon dioxide would be realeased into the atmosphere, time A or time B?
answer:

time A.