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.

Example Input: Background Paragraph: Besides anthropogenic productivity of the land, the biodiversity of degraded land also declines, as previously mentioned.[12] With less biodiversity, this ecosystem is less adaptable to when disasters strike it[11][8] It has a smaller available food supply, in terms of plants, for animals, who then may die out or more likely may relocate. Proof of this decline is that presently 15-20% of Tibetan Plateau species are now considered endangered; and now because of this animal and plant absence, the soil quality of these degraded lands is very poor.[1] It does not hold the necessary nutrients, such as water, nitrogen, and carbon, essential to either supporting life or inviting life back to that land.[6] As a result of such carbon and nitrogen loss in the Tibetan Plateau, $8,033/ha and $13,315/ha were respectively lost in economic terms. Soils are further weakened by dust storms whose frequency increases because of degradation.[11][4] Erosion of soil becomes a bigger problem, since no longer are there as many plants to anchor in the soil. In the northern Chinese province alone, 400 million are affected every year with an associated 54 billion yuan of annual economic loss due to grassland degradation.
Story: Xi province started sustainable agriculture and permaculture 40 years ago, while Huan province still uses conventional methods of cultivation. Animals grazing the fields extensively lead to desertification, the loss of carbon and nitrogen in the soil, and other problems. Permaculture was beneficial in Xi province, they re-built 10 inches of top soil in 10 years which is 6 times faster than the natural rate, which lead to a more diverse ecosystem and more biodiversity.
Question: Which province contributed to soil degradation less?
Example Output: Xi province.

Example Input: 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: Two neighboring countries France and Spain were competing for economical supremacy in Europe. Spain dug up fossil fuels and used it as an energy source. France used alternative sources of energy.
Question: Which country contributed more to climate change?
Example Output: Spain.

Example Input: Background Paragraph: If only 1.0 mL of 0.10 M hydrochloric acid is added to 1.0 L of pure water the pH drops drastically from 7.0 to 4.0. This is a 1000-fold increase in the acidity of the solution. For many purposes, it is desirable to have a solution which is capable of resisting such large changes in pH when relatively small amounts of acid or base are added to them. Such a solution is called a buffer. A buffer is a solution of a weak acid or a base and its salt. Both components must be present for the system to act as a buffer to resist changes in pH. Commercial buffer solutions, which have a wide variety of pH values, can be obtained.
Story: John is a scientist in a large pharmaceutical company. He devices many useful products using his knowledge of chemistry. Today, he has four solutions in front of him, solution A, solution B, solution C, and solution D. Solution A is a buffer, but solution B is not a buffer. Solution C is acidic, but solution D is not acidic. He needs to figure out what each solution does.
Question: Which solution may assist in changes in pH, solution A or solution B?
Example Output:
solution B.