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.

[EX Q]: Background Paragraph: Carbon monoxide is used in modified atmosphere packaging systems in the US, mainly with fresh meat products such as beef, pork, and fish to keep them looking fresh. The carbon monoxide combines with myoglobin to form carboxymyoglobin, a bright-cherry-red pigment. Carboxymyoglobin is more stable than the oxygenated form of myoglobin, oxymyoglobin, which can become oxidized to the brown pigment metmyoglobin. This stable red color can persist much longer than in normally packaged meat. Typical levels of carbon monoxide used in the facilities that use this process are between 0.4% to 0.5%. 
Story: Mike went to his local grocery store. He noticed that meats had two different packaging, product A and product B. When he looked closely, he found that in product A packaging carbon monoxide was used, but in product B carbon monoxide was not used. He asked the store clerk what difference it made. 
Question: Would product A look red longer or shorter than product B?
[EX A]: longer.

[EX Q]: Background Paragraph: Bernoulli’s law explains how the wings of both airplanes and birds create lift that allows flight (see Figure below ). The shape of the wings causes air to flow more quickly — and air pressure to be lower — above the wings than below them. This allows the wings to lift the plane or bird above the ground against the pull of gravity. A spoiler on a race car, like the one in Figure below , works in the opposite way. Its shape causes air to flow more slowly — and air pressure to be greater — above the spoiler than below it. As a result, air pressure pushes the car downward, giving its wheels better traction on the track. 
Story: Rob is experimenting with how air pressure works. To that end, he has designed two tests. In the first test the air flow works as it would in an airplane wing. He labels it as case A. In the second test the air flow works as it would in a race car spoiler. He labels it as case B. He is surprised to see that air flow behaves differently in different situations. 
Question: Would case A have higher or lower air pressure above it than case B?
[EX A]: lower.

[EX Q]: Background Paragraph: Weather conditions include air temperature, humidity, wind speed and direction, and precipitation. Weather is temporary. People in many states have the joke, "if you don't like the weather, wait five minutes and it will change." One way to change the weather is to have a different air mass move over the region. Interactions between air masses bring about a lot of weather. For example, thunderstorms and tornadoes form along a front. A front is where air masses meet. Fronts can bring about blizzards, thunderstorms, tornadoes and other types of weather. Weather prediction is much better than it was in past years. This is due in part to information from satellites. Climate is the long-term average of weather. The climate of a location depends on its latitude, position relative to the atmospheric circulation cells, position on a continent, altitude, and position relative to mountains. Areas with roughly the same climate make up a climate zone. The organisms that live within a climate zone create a unique biome. Earth's climate has changed throughout the planet's history. Earth was frigid at the end of the Pleistocene ice age, but has been warming since then. Since the Industrial Revolution the pace of warming has increased. In the past few decades the rate has really intensified. This is related to greenhouse gas emissions, primary from fossil fuel burning. The destruction of forests also increasing warming. The effects of global warming are already being seen. Treaties and voluntary actions are needed to reduce emissions to lessen the amount of global warming that will take place in the future. 
Story: Rob always confuses the terms climate and weather. He found it's better to compare them if he needs to learn more about their characteristics. To make things easier, he labeled the weather of his city as char A. Then he labeled the climate of this city as char B. Once finished with learning their characteristics, Rob focused on climate change issues. For that, he labeled the climate of present time as char C and climate just before industrial revolution as char D. 
Question: Does char A represent longer or shorter time period than char B?
[EX A]:
shorter.