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: Gasoline-powered vehicles emit a lot of harmful materials. Nitrogen oxides are formed when atmospheric nitrogen reacts with oxygen at the high temperatures found in a car engine. Carbon monoxide is a by-product of incomplete combustion of hydrocarbons. Evaporated and unused fuel releases volatile hydrocarbons into the atmosphere to help form smog. The presence of a catalytic converter in the exhaust system of the car causes these materials to react and be changed into less harmful products. 
Story: Blue island and Red island were two big sister islands situated 100 miles from each other. People on Blue island used gas powered vehicles, while people on Red island used electrical vehicles. The people on Blue island presented more respiratory problems. 
Question: Which island emitted fewer harmful materials?
answer:
Red.


question:
Background Paragraph: According to current definitions, all planets must revolve around stars; thus, any potential "rogue planets" are excluded. In the Solar System, all the planets orbit the Sun in the same direction as the Sun rotates (counter-clockwise as seen from above the Sun's north pole). At least one extrasolar planet, WASP-17b, has been found to orbit in the opposite direction to its star's rotation. The period of one revolution of a planet's orbit is known as its sidereal period or year. A planet's year depends on its distance from its star; the farther a planet is from its star, not only the longer the distance it must travel, but also the slower its speed, because it is less affected by its star's gravity. No planet's orbit is perfectly circular, and hence the distance of each varies over the course of its year. The closest approach to its star is called its periastron (perihelion in the Solar System), whereas its farthest separation from the star is called its apastron (aphelion). As a planet approaches periastron, its speed increases as it trades gravitational potential energy for kinetic energy, just as a falling object on Earth accelerates as it falls; as the planet reaches apastron, its speed decreases, just as an object thrown upwards on Earth slows down as it reaches the apex of its trajectory.Each planet's orbit is delineated by a set of elements:. 
Story: Planet Neptune is not only very cold but also farther from the Sun than the Earth. In fact, it is the farthest planet from the Sun in our solar system. On the other hand, the Earth enjoys a close proximity to the Sun. Only Mercury and Venus are closer to the Sun than the Earth. 
Question: Which planet would travel longer distance, Neptune or Earth?
answer:
Neptune.


question:
Background Paragraph: If a solution has a higher concentration of hydronium ions than pure water, it has a pH lower than 7. A solution with a pH lower than 7 is called an acid . As the hydronium ion concentration increases, the pH value decreases. Therefore, the more acidic a solution is, the lower its pH value is. Did you ever taste vinegar? Like other acids, it tastes sour. Stronger acids can be harmful to organisms. For example, stomach acid would eat through the stomach if it were not lined with a layer of mucus. Strong acids can also damage materials, even hard materials such as glass. 
Story: Alexiev and Sabrina were enthusiastic chemistry students completing the first experiment of their new course. They both started the experiment with pure water, and had to perform different experimental protocols to make changes to the water. At the end of the experiment, both of them measured the concentration of hydronium ions present in their reaction mixtures. Alexiev had a high concentration of hydronium ions present, while Sabrina had a low concentration present in her mixture. 
Question: Which person's mixture, Alexiev's or Sabrina's, is more acidic at the end?
answer:

Alexiev's.